This document provides an overview of pacemakers, including their indications, components, and modes of operation. It discusses the types of heart block that qualify as indications for pacemaker implantation. The components of a pacemaker system include the pulse generator which contains the battery and circuitry, and leads which deliver electrical impulses from the generator to the heart and sense cardiac activity. Pacemakers operate in different modes defined by which chambers they pace and sense from. Choosing the optimal pacing mode aims to increase heart rate, maximize stroke volume, use atrial-based pacing, and maintain normal ventricular activation sequence.
Speckle tracking echocardiography (STE) is an echocardiographic imaging technique that analyzes the motion of tissues in the heart by using the naturally occurring speckle pattern in the myocardium or blood when imaged by ultrasound.
Our concepts of heart disease are based on the enormous reservoir of physiologic and anatomic knowledge derived from the past 70 years' of experience in the cardiac catheterization laboratory.
As Andre Cournand remarked in his Nobel lecture of December 11, 1956, the cardiac catheter was the key in the lock.
By turning this key, Cournand and his colleagues led us into a new era in the understanding of normal and disordered cardiac function in huma
Based on the principle that the distal coronary pressure measured during vasodilation is directly proportional to maximum vasodilated perfusion.
FFR is defined as the ratio of maximum blood flow in a stenotic artery to maximum blood flow in the same artery if there were no stenosis.
FFR is simply calculated as a ratio of mean pressure distal to a stenosis (Pd) to the mean pressure proximal stenosis, that is the mean pressure in the aorta (Pa), during maximal hyperaemia.
Speckle tracking echocardiography (STE) is an echocardiographic imaging technique that analyzes the motion of tissues in the heart by using the naturally occurring speckle pattern in the myocardium or blood when imaged by ultrasound.
Our concepts of heart disease are based on the enormous reservoir of physiologic and anatomic knowledge derived from the past 70 years' of experience in the cardiac catheterization laboratory.
As Andre Cournand remarked in his Nobel lecture of December 11, 1956, the cardiac catheter was the key in the lock.
By turning this key, Cournand and his colleagues led us into a new era in the understanding of normal and disordered cardiac function in huma
Based on the principle that the distal coronary pressure measured during vasodilation is directly proportional to maximum vasodilated perfusion.
FFR is defined as the ratio of maximum blood flow in a stenotic artery to maximum blood flow in the same artery if there were no stenosis.
FFR is simply calculated as a ratio of mean pressure distal to a stenosis (Pd) to the mean pressure proximal stenosis, that is the mean pressure in the aorta (Pa), during maximal hyperaemia.
Its a medical presentation describing how to approach to various cardiac arrhythmias in systematic way. Illustrated with more ECG photographs from standard sources.
In these presentation we explained about basic require knowledge for ECG who were working in area of critical care, Casualty,ICU.
Here topic discussed is
Basic ECG
Presentation of each wave
Some basic findings
And how to interpret them.
All the major religions and belief systems in the UK support the principles of organ donation and transplantation and accept that organ donation is an individual choice.
We understand that you may have questions about whether your faith or beliefs affect your ability to become an organ donor. We're here to help support your decision, and have provided a selection of resources to help make sure you get the information you need.
Find out more about different attitudes to organ donation by selecting a faith or belief system below, or alternatively please consult the adviser from your religion or belief group.
Struggling with intense fears that disrupt your life? At Renew Life Hypnosis, we offer specialized hypnosis to overcome fear. Phobias are exaggerated fears, often stemming from past traumas or learned behaviors. Hypnotherapy addresses these deep-seated fears by accessing the subconscious mind, helping you change your reactions to phobic triggers. Our expert therapists guide you into a state of deep relaxation, allowing you to transform your responses and reduce anxiety. Experience increased confidence and freedom from phobias with our personalized approach. Ready to live a fear-free life? Visit us at Renew Life Hypnosis..
India Clinical Trials Market: Industry Size and Growth Trends [2030] Analyzed...Kumar Satyam
According to TechSci Research report, "India Clinical Trials Market- By Region, Competition, Forecast & Opportunities, 2030F," the India Clinical Trials Market was valued at USD 2.05 billion in 2024 and is projected to grow at a compound annual growth rate (CAGR) of 8.64% through 2030. The market is driven by a variety of factors, making India an attractive destination for pharmaceutical companies and researchers. India's vast and diverse patient population, cost-effective operational environment, and a large pool of skilled medical professionals contribute significantly to the market's growth. Additionally, increasing government support in streamlining regulations and the growing prevalence of lifestyle diseases further propel the clinical trials market.
Growing Prevalence of Lifestyle Diseases
The rising incidence of lifestyle diseases such as diabetes, cardiovascular diseases, and cancer is a major trend driving the clinical trials market in India. These conditions necessitate the development and testing of new treatment methods, creating a robust demand for clinical trials. The increasing burden of these diseases highlights the need for innovative therapies and underscores the importance of India as a key player in global clinical research.
Antibiotic Stewardship by Anushri Srivastava.pptxAnushriSrivastav
Stewardship is the act of taking good care of something.
Antimicrobial stewardship is a coordinated program that promotes the appropriate use of antimicrobials (including antibiotics), improves patient outcomes, reduces microbial resistance, and decreases the spread of infections caused by multidrug-resistant organisms.
WHO launched the Global Antimicrobial Resistance and Use Surveillance System (GLASS) in 2015 to fill knowledge gaps and inform strategies at all levels.
ACCORDING TO apic.org,
Antimicrobial stewardship is a coordinated program that promotes the appropriate use of antimicrobials (including antibiotics), improves patient outcomes, reduces microbial resistance, and decreases the spread of infections caused by multidrug-resistant organisms.
ACCORDING TO pewtrusts.org,
Antibiotic stewardship refers to efforts in doctors’ offices, hospitals, long term care facilities, and other health care settings to ensure that antibiotics are used only when necessary and appropriate
According to WHO,
Antimicrobial stewardship is a systematic approach to educate and support health care professionals to follow evidence-based guidelines for prescribing and administering antimicrobials
In 1996, John McGowan and Dale Gerding first applied the term antimicrobial stewardship, where they suggested a causal association between antimicrobial agent use and resistance. They also focused on the urgency of large-scale controlled trials of antimicrobial-use regulation employing sophisticated epidemiologic methods, molecular typing, and precise resistance mechanism analysis.
Antimicrobial Stewardship(AMS) refers to the optimal selection, dosing, and duration of antimicrobial treatment resulting in the best clinical outcome with minimal side effects to the patients and minimal impact on subsequent resistance.
According to the 2019 report, in the US, more than 2.8 million antibiotic-resistant infections occur each year, and more than 35000 people die. In addition to this, it also mentioned that 223,900 cases of Clostridoides difficile occurred in 2017, of which 12800 people died. The report did not include viruses or parasites
VISION
Being proactive
Supporting optimal animal and human health
Exploring ways to reduce overall use of antimicrobials
Using the drugs that prevent and treat disease by killing microscopic organisms in a responsible way
GOAL
to prevent the generation and spread of antimicrobial resistance (AMR). Doing so will preserve the effectiveness of these drugs in animals and humans for years to come.
being to preserve human and animal health and the effectiveness of antimicrobial medications.
to implement a multidisciplinary approach in assembling a stewardship team to include an infectious disease physician, a clinical pharmacist with infectious diseases training, infection preventionist, and a close collaboration with the staff in the clinical microbiology laboratory
to prevent antimicrobial overuse, misuse and abuse.
to minimize the developme
Navigating the Health Insurance Market_ Understanding Trends and Options.pdfEnterprise Wired
From navigating policy options to staying informed about industry trends, this comprehensive guide explores everything you need to know about the health insurance market.
Leading the Way in Nephrology: Dr. David Greene's Work with Stem Cells for Ki...Dr. David Greene Arizona
As we watch Dr. Greene's continued efforts and research in Arizona, it's clear that stem cell therapy holds a promising key to unlocking new doors in the treatment of kidney disease. With each study and trial, we step closer to a world where kidney disease is no longer a life sentence but a treatable condition, thanks to pioneers like Dr. David Greene.
Defecation
Normal defecation begins with movement in the left colon, moving stool toward the anus. When stool reaches the rectum, the distention causes relaxation of the internal sphincter and an awareness of the need to defecate. At the time of defecation, the external sphincter relaxes, and abdominal muscles contract, increasing intrarectal pressure and forcing the stool out
The Valsalva maneuver exerts pressure to expel faeces through a voluntary contraction of the abdominal muscles while maintaining forced expiration against a closed airway. Patients with cardiovascular disease, glaucoma, increased intracranial pressure, or a new surgical wound are at greater risk for cardiac dysrhythmias and elevated blood pressure with the Valsalva maneuver and need to avoid straining to pass the stool.
Normal defecation is painless, resulting in passage of soft, formed stool
CONSTIPATION
Constipation is a symptom, not a disease. Improper diet, reduced fluid intake, lack of exercise, and certain medications can cause constipation. For example, patients receiving opiates for pain after surgery often require a stool softener or laxative to prevent constipation. The signs of constipation include infrequent bowel movements (less than every 3 days), difficulty passing stools, excessive straining, inability to defecate at will, and hard feaces
IMPACTION
Fecal impaction results from unrelieved constipation. It is a collection of hardened feces wedged in the rectum that a person cannot expel. In cases of severe impaction the mass extends up into the sigmoid colon.
DIARRHEA
Diarrhea is an increase in the number of stools and the passage of liquid, unformed feces. It is associated with disorders affecting digestion, absorption, and secretion in the GI tract. Intestinal contents pass through the small and large intestine too quickly to allow for the usual absorption of fluid and nutrients. Irritation within the colon results in increased mucus secretion. As a result, feces become watery, and the patient is unable to control the urge to defecate. Normally an anal bag is safe and effective in long-term treatment of patients with fecal incontinence at home, in hospice, or in the hospital. Fecal incontinence is expensive and a potentially dangerous condition in terms of contamination and risk of skin ulceration
HEMORRHOIDS
Hemorrhoids are dilated, engorged veins in the lining of the rectum. They are either external or internal.
FLATULENCE
As gas accumulates in the lumen of the intestines, the bowel wall stretches and distends (flatulence). It is a common cause of abdominal fullness, pain, and cramping. Normally intestinal gas escapes through the mouth (belching) or the anus (passing of flatus)
FECAL INCONTINENCE
Fecal incontinence is the inability to control passage of feces and gas from the anus. Incontinence harms a patient’s body image
PREPARATION AND GIVING OF LAXATIVESACCORDING TO POTTER AND PERRY,
An enema is the instillation of a solution into the rectum and sig
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CRISPR-Cas9, a revolutionary gene-editing tool, holds immense potential to reshape medicine, agriculture, and our understanding of life. But like any powerful tool, it comes with ethical considerations.
Unveiling CRISPR: This naturally occurring bacterial defense system (crRNA & Cas9 protein) fights viruses. Scientists repurposed it for precise gene editing (correction, deletion, insertion) by targeting specific DNA sequences.
The Promise: CRISPR offers exciting possibilities:
Gene Therapy: Correcting genetic diseases like cystic fibrosis.
Agriculture: Engineering crops resistant to pests and harsh environments.
Research: Studying gene function to unlock new knowledge.
The Peril: Ethical concerns demand attention:
Off-target Effects: Unintended DNA edits can have unforeseen consequences.
Eugenics: Misusing CRISPR for designer babies raises social and ethical questions.
Equity: High costs could limit access to this potentially life-saving technology.
The Path Forward: Responsible development is crucial:
International Collaboration: Clear guidelines are needed for research and human trials.
Public Education: Open discussions ensure informed decisions about CRISPR.
Prioritize Safety and Ethics: Safety and ethical principles must be paramount.
CRISPR offers a powerful tool for a better future, but responsible development and addressing ethical concerns are essential. By prioritizing safety, fostering open dialogue, and ensuring equitable access, we can harness CRISPR's power for the benefit of all. (2998 characters)
How many patients does case series should have In comparison to case reports.pdfpubrica101
Pubrica’s team of researchers and writers create scientific and medical research articles, which may be important resources for authors and practitioners. Pubrica medical writers assist you in creating and revising the introduction by alerting the reader to gaps in the chosen study subject. Our professionals understand the order in which the hypothesis topic is followed by the broad subject, the issue, and the backdrop.
https://pubrica.com/academy/case-study-or-series/how-many-patients-does-case-series-should-have-in-comparison-to-case-reports/
22. Pacemaker Indication Classifications
Class I – Conditions for which there is evidence and/or
general agreement that permanent pacemakers should be
implanted
Class II – Conditions for which permanent pacemakers are
frequently used but there is divergence of opinion with
respect to the necessity of their insertion
– Class IIa: Weight of evidence/opinion is in favor of
usefulness/efficacy
– Class IIb: Usefulness/efficacy is less well established
by evidence/opinion
Class III – Conditions for which there is general agreement
that pacemakers are unnecessary
JACC Vol. 31, no. 5 April 1998, 1175-1209
23. Pacemaker Indication Classifications
• Evidence supporting current recommendations are
ranked as levels A, B, and C:
– Level A: Data derived from multiple randomised clinical
trials involving a large number of individuals
– Level B: Data derived from a limited number of trials
involving comparatively small numbers of patients or
from well-designed data analysis of nonrandomised
studies or observational data registries
– Level C: Consensus of expert opinion was the primary
source of recommendation
JACC Vol. 31, no. 5 April 1998, 1175-1209
25. Class I Indications
• Sinus node dysfunction with documentedSinus node dysfunction with documented symptomatic sinussymptomatic sinus
bradycardiabradycardia
• Symptomatic chronotropic incompetence
Class II Indications
• Class IIa: Symptomatic patients with sinus node dysfunction
and with no clear association between symptoms and
bradycardia
• Class IIb: Chronic heart rate < 30 bpm in minimally
symptomatic patients while awake
Class III Indications
• Asymptomatic sinus node dysfunction
Sinus Node Dysfunction –
Indications for Pacemaker Implantation
JACC Vol. 31, no. 5 April 1998, 1175-1209
26. Sinus Node Dysfunction –
Sinus Bradycardia
• Persistent slow rate from the SA node. The
parameters from this waveform include:
– Rate = 55 bpm
– PR interval = 180 ms (0.18 seconds)
27. Sinus Node Dysfunction –
Sinus Arrest
• Failure of sinus node discharge resulting in the absence
of atrial depolarisation and periods of ventricular
asystole
– Rate = 75 bpm
– PR interval = 180 ms (0.18 seconds)
– 2.8 second arrest
2.8-second arrest
28. 2.1-second pause
Sinus Node Dysfunction –
SA Exit Block
• Transient blockage of impulses from the SA
node
– Rate = 52 bpm
– PR interval = 180 ms (0.18 seconds)
– 2.1-second pause
29. Sinus Node Dysfunction –
Brady-Tachy Syndrome
• Intermittent episodes of slow and fast rates
from the SA node or atria
– Rate during bradycardia = 43 bpm
– Rate during tachycardia = 130 bpm
31. AV Block
• First-degree AV block
• Second-degree AV
block
– Mobitz types I and II
• Third-degree AV block
32. Class I Indications
• 3rddegree AV block associated with:
– Symptomatic bradycardia (including those from arrhythmias
and other medical conditions)
– Documented periods of asystole > 3 seconds
– Escape rate < 40 bpm in awake, symptom-free patients
– Post AV junction ablation
– Post-operative AV block not expected to resolve
• Second degree AV block regardless of type or site of
block, with associated symptomatic bradycardia
AV Block – Indications
JACC Vol.. 31, no. 5 April 1998, 1175-1209
33. AV Block – Indications
JACC Vol. 31, no. 5 April 1998, 1175-1209
Class II Indications
• Class IIa:
– Asymptomatic CHB with a ventricular rate > 40 bpm
– Asymptomatic Type II 2nd degree AV block
– Asymptomatic Type I 2nddegree AV block within the His-Purkinje
system found incidentally at EP study
– First-degree AV block with symptoms suggestive of pacemaker
syndrome and documented alleviation of symptoms with temporary AV
pacing
• Class IIb:
– First degree AV block > 300 ms in patients with LV dysfunction in whom
a shorter AV interval results in haemodynamic improvement
34. AV Block – Indications
Class III Indications
• Asymptomatic 1stdegree AV block
• Asymptomatic Type I 2nd degree AV
block at supra-Hisian level
• AV block expected to resolve and
unlikely to recur (e.g., drug toxicity,
Lyme Disease)
JACC Vol. 31, no. 5 April 1998, 1175-1209
35. First-Degree AV Block
• AV conduction is delayed, and the PR
interval is prolonged (> 210 ms or 0.21
seconds)
– Rate = 79 bpm
– PR interval = 340 ms (0.34 seconds)
340 ms
36. Second-Degree AV Block –
Mobitz I (Wenckebach)
• Progressive prolongation of the PR interval until a
ventricular beat is dropped
– Ventricular rate = irregular
– Atrial rate = 90 bpm
– PR interval = progressively longer until a P-wave
fails to conduct
200 360 400
ms ms ms
No
QRS
37. Second-Degree AV
Block – Mobitz II
• Regularly dropped ventricular beats
– 2:1 block (2 P waves to 1 QRS complex)
– Ventricular rate = 60 bpm
– Atrial rate = 120 bpm
P P QRS
38. Third-Degree AV Block
• No impulse conduction from the atria to the
ventricles
– Ventricular rate = 37 bpm
– Atrial rate = 130 bpm
– PR interval = variable
40. Class I Indications
• Intermittent 3rddegree AV block
• Type II 2nd degree AV block
Class II Indications
• Class IIa:
– Syncope not proved to be due to AV block when other causes have been exluded,
specifically VT
– Prolonged HV interval ( >100 ms)
– Pacing-induced infra-Hisian block that is not physiological
• Class IIb: None
Class III Indications
• Asymptomatic fascicular block without AV block
• Asymptomatic fascicular block with 1st degree AV block
Bifascicular and Trifascicular
Block (Chronic) – Indications
JACC Vol. 31, no. 5 April 1998, 1175-1209
44. Trifascicular Block
• Complete block in
the right bundle
branch and
complete or
incomplete block in
both divisions of the
left bundle branch
45. ECG Recording:
• Rate
• Rhythm
–regular or irregular?
–if irregular, is there a pattern?
(e.g. 2:1 or 3:1 block or Wenckebach)
• QRS-complexes? Width?
• P-waves? In what relation to QRS-complexes?
• PR-Interval with normal duration (120-210 ms) or
irregular? Continuously increasing P-R interval?
49. • Pulse generator: power
source or battery
• Leads or wires
• Cathode (negative
electrode)
• Anode (positive
electrode)
• Body tissue
IPG
Lead
Anode
Cathode
Implantable Pacemaker Systems Contain the
Following Components:
50. • Contains a battery
that provides the
energy for sending
electrical impulses
to the heart
• Houses the circuitry
that controls
pacemaker
operations
Circuitry
Battery
The Pulse Generator:
63. Heart Rate
x
x
x
x
SV
x HR
Age 65-80 (N=16)
130
120
110
100
90
80
70
HeartRate(BPM)
StrokeVolume(mL/Min)
Cardiac Output (L/Min)
Rodehefer RJ, Circ.; 69:203, 1984.
6 7 8 9 10 11 12 13 14 15 1613 17 18
70
80
90
100
110
120
130
140
150
160
x
64. Proven Benefits of Atrial Based
Pacing
Study Results
Higano et al. 1990
Gallik et al. 1994
Santini et al. 1991
Rosenqvist et al. 1991
Sulke et al. 1992
Improved cardiac index during low level
exercise (where most patient activity occurs)
Increase in LV filling
30% increase in resting cardiac output
Decrease in pulmonary wedge pressure
Increase in resting cardiac output
Increase in resting cardiac output, especially
in patients with poor LV function
Decreased incidence of mitral and tricuspid
valve regurgitation
65. Proven Benefits of Atrial Based
Pacing
Study Results
Rosenquist 1988
Santini 1990
Stangl 1990
Zanini 1990
Less atrial fibrillation (AF), less CHF, improved
survival after 4 years compared to VVI
Less AF, improved survival after 5 years average
Less AF, improved survival after 5 years
compared to VVI
Suppression of atrial dysrhythmias
Improved morbidity (less AF, CHF, embolic
events) after 3 plus uears, compared to VVI
66. Patient Mode Preference
DDDR 59%
DDIR 13%
Any Dual 9%
No Preference 9%
DDD 5%
VVIR 5%
Sulke N, et al. J AM Coll Cardiol; 17(3):696-706, 1991
70. Mode Selection Decision Tree
DDIR with
SV PVARP
DDDR with
MS
N
VVI
VVIR
Are they
chronic?
Y
Y N
DDD, VDD
DDDR DDDR
Y N
Is AV conduction
intact?
Is SA node function
presently adequate?
Symptomatic
bradycardia
Are atrial
tachyarrhythmias
present?
Is SA node function
presently adequate?
Is AV conduction
intact?
Y
Y N
AAIR
DDDR
DDD, DDI
with RDR
N N(SSS)
(CSS,
VVS)
N
71. Summary of Pacemaker Indications
• Sinus node dysfunction
• AV block (Congenital, acquired, surgical)
• Bifascicular and trifascicular block
• Hypersensitive Carotid Sinus Syndrome (CSS)
• [ Malignant Vasovagal Syncope (MVVS) ]
• Pacing after cardiac transplantation
• Heart Failure / HOCM / AF
• ( AHA/ACC and BPEG indications )
We will start by discussing normal impulse fomation and then move into common conduction disturbances. As abnormal conduction is discussed we will correlate the AHA/ACC guidelines for pacemaker implantation related to that particular rhythm.
Initiation of the cardiac cycle normally begins with initiation of the impulse at the sinoatrial (SA) node. A resulting wave of depolarization passes through the right and left atria, which produces the P wave on the surface ECG and stimulates atrial contraction.
Following activation of the atria, the impulse proceeds to the atrioventricular (AV) node, which is the only normal conduction pathway between the atria and the ventricles. The AV node slows impulse conduction which allows time for contraction of the atria and the pumping of blood from the atria to the ventricles prior to ventricular contraction. Conduction time through the AV node accounts for most of the duration of the PR interval.
Just below the AV node, the impulse passes through the bundle of His. A small portion of the last part of the PR interval is represented by the conduction time through the bundle of His.
After the impulse passes through the bundle of His, it proceeds through the left and right bundle branches. A small portion of the last part of the PR interval is represented by the conduction time through the bundle branches.
Next the impulse passes through the Purkinje fibers (interlacing fibers of modified cardiac muscle). A small portion of the last part of the PR interval is represented by the conduction time through the Purkinje system.
The impulse passes quickly through the bundle of His, the left and right bundle branches, and the Purkinje fibers leading to depolarization and contraction of the ventricles. The QRS complex on the ECG represents the depolarization of the ventricular muscle mass.
The T wave on the ECG represents the repolarization and relaxation of the ventricles.
Atrial repolarization and relaxation occurs during the QRS complex.
The American College of Cardiology and the American Heart Association have determined guidelines for pacemaker implantation. These 1998 guidelines are divided into three classes. Class II has subcategories A and B.
Gregoratos G, et al. ACC/AHA guidelines for Implantation of cardiac pacemakers and antiarrhythmia devices: a report of the ACC/AHA Task Force on Practice Guidelines (Committee on Pacemaker Implantation). J Am Coll Cardiol. 1998:31; 1175-1206.
In addition to classification, recommendations that are evidence based were added to descriptions. For example:
Class I indication for symptomatic third-degree AV block was designated with a “level of evidence: C”
For the sake of brevity, this presentation will not include evidence based recommendations. For a complete listing of recommendations, consult JACC , April 1998.
Gregoratos G, et al. ACC/AHA guidelines for Implantation of cardiac pacemakers and antiarrhythmia devices: a report of the ACC/AHA Task Force on Practice Guidelines (Committee on Pacemaker Implantation). J Am Coll Cardiol. 1998:31; 1175-1206.
Sinus node dysfunction encompasses a variety of impulse formation and conduction problems, including:
sinus bradycardia
sinus arrest
sinoatrial block
supraventricular tachycardias alternating with periods of bradycardia or asystole
chronotropic incompetence
When symptoms are present, the term sick sinus syndrome (SSS) is also used.
Note: As many as 30% of patients will have additional conduction abnormalities elsewhere in the conduction system.
Class I Indication(s):
1. Documented symptomatic sinus bradycardia, including frequent sinus pauses that produce symptoms. May be due to long-term drug therapy of a type and dose for which there is no accepted alternative
2. Symptomatic chronotropic incompetence (of the sinus node)
Class II Indication(s):
1a.Symptomatic patients with sinus node dysfunction and documented rates of &lt; 40 bpm without a clear-cut association between significant symptoms and the bradycardia
1b.In minimally symptomatic patients, chronic heart rate &lt; 30 bpm while awake
Class III Indication(s):
1. Asymptomatic sinus node dysfunction (sinus bradycardia, SA block, or sinus arrest). Also, sinus node dysfunction with symptomatic bradycardia due to nonessential drug therapy
2. Sinus node dysfunction in patients with symptoms suggestive of bradycardia that are clearly documented as not associated with a slow heart rate
Gregoratos G, et al. ACC/AHA guidelines for Implantation of cardiac pacemakers and antiarrhythmia devices: a report of the ACC/AHA Task Force on Practice Guidelines (Committee on Pacemaker Implantation). J Am Coll Cardiol. 1998:31; 1175-1206.
Sinus bradycardia occurs when the SA node fires at a slow (&lt; 60 bpm) rate.
Sinus arrest occurs when there is a pause in the rate at which the SA node fires. With sinus arrest there is no relationship between the pause and the basic cycle length.
SA exit block occurs when the SA node fires, but the impulse does not conduct to the pathways that cause the atrium to contract. In SA exit block there is a relationship between the pattern and the basic cycle length (because the sinus node continues to fire regularly), approximately two, but less commonly three or four times the normal P-P interval.
Brady-tachy syndrome occurs when the SA node has alternating periods of firing too slowly (&lt; 60 bpm) and too fast (&gt; 100 bpm). Brady-tachy syndrome often manifests itself in periods of atrial tachycardia, flutter, or fibrillation. Cessation of the tacycardia is often followed by long pauses from the SA node.
It is important to be able to able to increase heart rate with activity (chronotropic competence). The pacemaker and mode selected should provide the ability to increase rate with activity either by “tracking” the sinus node or, if the sinus node is not chronotropically competent, by providing the rate response via a sensor.
AV block can manifest in the following ways listed above.
Class I Indication(s):
In addition to those listed, other indications for 3rd degree block include:
Neuromuscular diseases with AV block such as myotonic muscular dystrophy, Kearns-Sayre syndrome, Erb’s dystrophy, and peroneal muscular atrophy.
Gregoratos G, et al. ACC/AHA guidelines for Implantation of cardiac pacemakers and antiarrhythmia devices: a report of the ACC/AHA Task Force on Practice Guidelines (Committee on Pacemaker Implantation). J Am Coll Cardiol. 1998:31; 1175-1206.
In addition to those listed, other indications include:
Class II Indication(s):
IIa: Asymptomatic Type II 2° AV block. If not paced, asymptomatic Type II 2° AV block patients should be followed very closely because Type II 2° AV block patients with symptoms are at a high risk for developing CHB. Most patients with type II block are symptomatic, which is a Class I indication. True asymptomatic Type II block is rare and pacemaker therapy is generally recommended.
IIb: Marked first-degree AV block in patients with LV dysfunction and symptoms of congestive heart failure in whom a shorter AV interval results in hemodynamic improvement, presumably by decreasing left atrial filling pressure.
Gregoratos G, et al. ACC/AHA guidelines for Implantation of cardiac pacemakers and antiarrhythmia devices: a report of the ACC/AHA Task Force on Practice Guidelines (Committee on Pacemaker Implantation). J Am Coll Cardiol. 1998:31; 1175-1206.
AV block can be described as a prolongation of the PR interval. The PR interval is the interval from the onset of the P wave to the onset of the QRS complex. First-degree AV block is defined by a PR interval greater than 0.20 seconds (200 msec). First-degree AV block can be thought of as a delay in AV conduction, but each atrial signal is conducted to the ventricles (1:1 ratio).
Second-degree AV block is characterized by intermittent failure of atrial depolarizations to reach the ventricle. There are two patterns of second-degree AV block. The first, Type I, is marked by progressive prolongation of the PR interval in cycles preceding a dropped beat. This is also referred to as Wenckebach or Mobitz Type I block.
The AV node is most commonly the site of Mobitz I block. The QRS duration is usually normal.
Mobitz Type II second-degree AV block refers to intermittent dropped beats preceded by constant PR intervals. To differentiate Mobitz I from Mobitz II, note the PR interval in the beats preceding and following the dropped beat. If a difference between these two PR intervals is more than 0.02 seconds (20 msec), then it is Mobitz I. If the difference is less than 0.02 seconds, then it is Mobitz II.
The infranodal (His bundle) tissue is most commonly the site of Mobitz II block.
Note: Advanced second-degree block refers to the block of two or more consecutive P waves (i.e., 3:1 block).
Third-degree AV block is also referred to as complete heart block. It is characterized by a complete dissociation between P waves and QRS complexes. The QRS complexes are not caused by conduction of the P waves through the AV node to the ventricles, but rather the QRS is initiated at a site below the AV node (such as in the His bundle or the Purkinje fibers). This “escape rhythm” is normally 40–60 bpm if initiated by the His bundle (a junctional rhythm) and &lt;40 bpm if initiated by the Purkinje fibers.
After the impulse passes through the bundle of His, it proceeds through the left and right bundle branches. A small portion of the last part of the PR interval is represented by the conduction time through the bundle branches.
Symptomatic advanced AV block that develops in patients with underlying bifascicular and trifascicular block is associated with a high mortality rate and a significant incidence of sudden death, though there is evidence of a slow rate of progression to 3rd degree AV block.
Syncope is common in patients with bifascicular block, and evidence proves an increased incidence of sudden cardiac death. Therefore, if the cause of syncope in the presence of bi/trifascicular block cannot be determined, prophylactic pacing is indicated.
PR and HV intervals have been identified as possible predictors of 3rd degree AV block and sudden death in the presence of underlying bifascicular block. However, the prolongation is often at the level of the AV node, and frequently there is no correlation between the PR and HV intervals and progression to 3rd degree AV block and the incidence of sudden cardiac death.
Gregoratos G, et al. ACC/AHA guidelines for Implantation of cardiac pacemakers and antiarrhythmia devices: a report of the ACC/AHA Task Force on Practice Guidelines (Committee on Pacemaker Implantation). J Am Coll Cardiol. 1998:31; 1175-1206.
Bifascicular block is defined as one of the following:
Right bundle branch block and left posterior hemiblock (highlighted in red)
Right bundle branch block and left anterior hemiblock
Complete left bundle branch block
Bifascicular block is marked by prolonged QRS (&gt; 120 ms or .12 seconds or longer).
Bifascicular block
Right bundle branch block and left anterior hemiblock (highlighted in red and yellow)
Bifascicular block
Complete left bundle branch block (highlighted red)
Trifascicular Block has the appearance of AV nodal block. Combinations that constitute trifascicular block are:
Right bundle branch block, complete left anterior fascicular block and complete left posterior fascicular block.
Combination of complete block in one or two subdivisions of the common bundle and incomplete block in one or two subdivisions.
Lithium-iodine is the most commonly used power source for today’s pacemakers. Microprocessors (both ROM and RAM) control sensing, output, telemetry, and diagnostic circuits.
The first implantable pacemakers, developed in 1960, were asynchronous pacemakers, i.e., pacing without regard to the heart’s intrinsic action (VOO).
Single-chamber “demand” pacemakers were introduced in the late 1960s.
In 1979, the first dual chamber pacemaker (DVI) was introduced, followed closely by the 1981 release of the first DDD pacemaker, the Versatrax.
The first single chamber, rate responsive pacemaker, Activitrax, was released in 1985.
Today, dual-chamber pacemakers use rate responsive pacing to mimic the heart’s rate response to provide/meet metabolic needs, most recently using a combination of sensors to best accomplish this task…
Pictured above:
(upper left) One of the first implantable devices. The device is coated with epoxy.
(upper right) Chardack Greatbatch device, late 1960’s.
(lower left) Model 5943, a VVI device with titanium case (1974).
(Middle) One of the first DDD devices, model number 7004.
(lower right) Early 1998: Kappa 400!
This slide illustrates the essential components of a pacing lead.
The following topics will be discussed for each component:
· Purpose
· Design factors
· Performance factors
The first letter refers to the chamber(s) being paced
The second letter refers to the chamber(s) being sensed
The third letter refers to the pacemaker’s response to a sensed event:
T = TriggeredD = Dual (inhibited and triggered*)
I = InhibitedO = No response
*In a single chamber mode, “triggered” means that when an intrinsic event is sensed, a pace is triggered immediately thereafter. In a dual chamber mode, “triggered” means that a sensed atrial event will initiate (trigger) an A-V delay.
The fourth letter denotes the pacemaker’s programmability and whether it is capable of rate response:
P = Simple Programmable (rate and/or output)
M = Multiprogrammable (rate, output, sensitivity, etc.)
C = Communicating (pacemaker can send/receive information to/from the programmer)
R = Rate Modulation
O = None
Note that this sequence is hierarchical. In other words, it is assumed that if a pacemaker has rate modulation capabilities, “R”, that it also can communicate, “C”.
The fifth letter represents the pacemaker’s antitachycardia functions:
P = PaceD = Dual (pace and shock available)
S = ShockO = None
You may want to test the audience by having them describe different pacing modes. More modes and ECG strips are found in Module 2.
In order to choose the mode for the patient that will optimize pacing therapy, we need to think about four factors which can be influenced by the pacemaker:
Heart rate
Stroke volume
Atrial electrical stability
Ventricular activation sequence
Cardiac output is the result of heart rate (HR) times stroke volume (SV). In most cases, pacemaker patients have diseased hearts, and cardiac output has been compromised by reduced heart rate and/or stroke volume. Improved (ideally, normal) cardiac output is the primary goal of optimal pacing therapy.
When selecting lower rate and rate response parameter values, it is important to select rates that are appropriate for the condition of the patient. If paced rates are too fast, it is possible to overload the venous system, which may cause negative results such as stretching of the atrium, increased edema, and increased congestion (patients may complain of palpitations or their hearts “racing”). If paced rates are achieved that are not fast enough for a given activity, the peripheral demands will exceed the cardiac output that is provided and the patient will have to curtail activity.
In a healthy heart, cardiac output at maximum workload can reach a level approximately 4.5 times that at rest. Increases in heart rate (workload) alone can increase cardiac output by 300% (3 times), and increases in stroke volume can increase cardiac output by 50%.
In the pacing population, ability to increase SV is usually diminshed. Therefore, it is important to be able to increase heart rate with activity or to meet metabolic need.
Rodeheffer R, et al. Exercise cardiac output is maintained with advancing age in healthy human subjects: cardiac dilation and increased stroke volume compensate for a diminished heart rate. Circulation, 1984; 69(2), 203-213.
Included is a summary of some studies depicting long-term results of AV synchronous (atrial based) and non-synchronous (VVI/R) pacing
In addition to heart rate and stroke volume, the propensity for development of atrial fibrillation with the associated risks of thromboembolic events, stroke, and reduced survival is an important issue. Studies have shown that atrial-based pacing modes (modes that can sense and respond to P waves) have a much lower incidence of developing atrial fibrillation than modes that only pace and sense in the ventricle. For this reason, as well as the increase in cardiac output due to AV synchrony, it is advantageous to use atrial-based pacing modes whenever possible.
Note: Exceptions include instances when it is not possible to sense the atrium or conditions in which it would not be beneficial to sense the atrium, such as chronic atrial fibrillation or flutter, inability to achieve adequate pacing/sensing thresholds, or an inexcitable atrium.
Higano, et al. Hemodynamic importance of atrioventricular synchrony during low levels of exercise. PACE, 1990; 13:509 Abstact.
Gallik DM, et al. Comparison of ventricular function in atrial rate adaptive versus dual chamber rate adaptive pacing during exercise. PACE, 1994; 17(2):179-185
Santini, et al. New Perspectives in Cardiac Pacing. Mount Kisco, NY: Futura Publishing, 1991.
Rosenquist M, et al. Relative importance of activation sequence compared to atrioventricular synchrony during low levels of exercise. AM J Cardiology, 1991;67:148-156.
SulkeN, et al. “Sbuclinical pacemaker syndrome: A randomized study of symptom free patients with ventricular demand (VVI) pacemakers upgraded to dual chamber devices. Brit Heart J, 1992; 67(1):57-64.
In addition to heart rate and stroke volume, the propensity for development of atrial fibrillation with the associated risks of thromboembolic events, stroke, and reduced survival is an important issue. Studies have shown that atrial-based pacing modes (modes that can sense and respond to P waves) have a much lower incidence of developing atrial fibrillation than modes that only pace and sense in the ventricle. For this reason, as well as the increase in cardiac output due to AV synchrony, it is advantageous to use atrial-based pacing modes whenever possible.
Note: Exceptions include instances when it is not possible to sense the atrium or conditions in which it would not be beneficial to sense the atrium, such as chronic atrial fibrillation or flutter, inability to achieve adequate pacing/sensing thresholds, or an inexcitable atrium.
Rosenquist M, et al. Long-term pacing in sinus node disease: Effects of stimulation mode on cardiovascular morbidity and mortality. AM Heart J. 1988; 116(1 pt.1): 16-22.
Santini M., et al. Relation of prognosis in sick sinus syndrome to age, conduction defects, and modes of permanent cardiac pacing. AM J Cardiol. 1990; 65(11):729-735.
Stangl K, et al. Differences between atrial single chamber pacing (AAI) and ventricular single chamber acing (VVI) with respect to prognosis and antiarrhythmic effect in patients with SSS. PACE, 1990; 13(12):863-868.
Zanini R, et al. Morbidity and mortality of patients with sinus node disease: comparative effects of atrial and ventricular pacing. PACE, 1990; 13(12): 2076-2079.
Subjective Patient Improvement
Several studies have compared dual chamber and/or atrial pacing to ventricular pacing in terms of patient preference and other quality of life indicators. Overwhelmingly, patients choose dual chamber pacing over VVI/R, and conversely, most patients identify VVI/R as the least acceptable pacing mode.
Sulke N, et al. A randomized double-blind crossover comparison of four rate-reponsive pacing modes. JACC, 1991; 17(3):696-706.
This is the decision tree that we will be using to (practice) determine the optimal pacing mode for five example patients. When evaluating which pacing mode would provide optimal pacing therapy for each patient, we must ask ourselves three questions:
Are atrial tachyarrhythmias present? (Can the atrium be paced and sensed reliably?)
Is AV conduction intact?
Is SA node function presently adequate?
