Approach to a patient with Heart rate abnormality in ECG

Fundamentals of ECG
Abnormal Heart Rate
Dr. Md.Toufiqur Rahman
MBBS, FCPS, MD, FACC, FESC, FRCP, FSCAI,
FCCP,FAPSC, FAPSIC, FAHA,FACP
Professor & head of Cardiology
CMMC, Manikganj
Ex professor of cardiology,
NICVD, Dhaka

Fundamentals of ECG
IFMSA Bangladesh
Heart rate abnormalities
18/06/2020 at 8-9 pm
Case-1: ECG with NSR
Case-2: ECG with sinus
bradycardia
tachycardia
arrhythmia
Determining heart rate
Normal heart rate in adults
Normal heart rate in children
Characteristics of NSR
Factors that can change heart
rate
Variations on sinus rhythm
Sinus arrhythmia
Sinus bradycardia
Sinus tachycardia
INAPPROPRIATE SINUS
Tachycardia

Fundamentals of ECG
Case-1: A 45 years
old man
presented with
chest discomfort
on exertion and
occasional
palpitation for
last 3 months. His
pulse 76/min, BP-
130/80 mm Hg.
He had the
following ECG.

Fundamentals of ECG
A 48 years old
lady presented
with weight gain,
leg edema, cold
intolerance and
generalized
weakness for last
6 months. Her
pulse 50/min, BP-
150/85 mm Hg.
She had the
following ECG.

Fundamentals of ECG
A 21 years old
medical student
presented with chest
tightness,
palpitations and
vomiting before his
professional
examination. His
pulse 105/min, BP-
110/75 mm Hg. On
emergency
department, he had
the following ECG.

Fundamentals of ECG
A 14 years old boy presented with occasional palpitations and chest
discomfort for last several months . His pulse 105/min, BP-110/75 mm
Hg. On emergency department, he had the following ECG.

Fundamentals of ECG
Determining Heart Rate
• There are two different rates that can be determined on
ECGs.
• The atrial rate is indicated by the frequency of the P
waves and the ventricular rate is indicated by the
frequency of the QRS complexes.
• Normally, the atrial rate should be the same as the
ventricular rate in the absence of disease, however
certain conditions, such as third degree AV nodal block or
ventricular tachycardia can alter this normal relationship
causing “AV dissociation”.
• In this setting, the atrial rate (P waves) and ventricular
rate (QRS complexes) are at different heart rates.

Fundamentals of ECG

• One quick and easy way to determine the ventricular
rate is to examine the RR interval (distance between
two consecutive R waves) and use a standard scale to
find the rate. This is called ‘The Square counting
method’
• If two consecutive R waves are separated by only one
large box, then the rate is 300 beats per minute.
• If the R waves are separated by two large blocks, then
the ventricular rate is 150 beats per minute.
• The scale continues down to show that if two
consecutive R waves are separated by 8 large boxes,
then the rate is 37 beats per minute.
Fundamentals of ECG

• Use the sequence 300-150-100-75-60-50-43-37. When the
second QRS complex is between two lines, take the mean
of the two numbers from the sequence or use the fine-
tuning method.
• The 'square counting' method can be fine-tuned with the
following sequence
300-250-214-187-167-150-136-125-115-107-100-94-88-
83-79-75-71-68-65-62-60.
• Another quick way to calculate the rate is based on the
fact that the entire ECG is 10 seconds. So by counting the
number of QRS complexes and multiplying by 6, the
number per minute can be calculated (since 10 seconds
times 6 is 60 seconds or 1 minute).
Fundamentals of ECG

• The marker method: Non-regular rhythms are best determined
with the "3 second marker method". Count the number of QRS
complexes that fit into 3 seconds (some ECG writers print this
period on the ECG paper). Multiply this number by 20 to find the
number of beats/minute.
• This is a better method when the QRS complexes are irregular
making the first method less accurate, since the RR intervals may
vary from beat to beat in this setting.
• If a different paper speed is used, calculations will have to be
modified appropriately. Calculate atrial and ventricular rates
separately if they are different (e.g. complete heart block)
• The machine reading can also be used and is usually correct —
however, it may occasionally be inaccurate in the presence of
abnormal QRS/T-wave morphology, e.g. may count peaked T
waves as QRS complexes or miss QRS complexes with reduced
amplitude.
Fundamentals of ECG

Fundamentals of ECG
There are multiple methods to estimate the rate:
• We can calculate the beats per minute (bpm) by dividing 1500 by the number
of SMALL squares between two R waves (R-R interval = one beat)
• We can calculate the beats per minute (bpm) by dividing 300 by the number
of LARGE squares between two R waves (R-R interval = one beat)
• REGULAR rhythms
Rate = 300 / number of LARGE squares between consecutive R waves.
• Very FAST rhythms:
Rate = 1500 / number of SMALL squares between consecutive R waves.
• SLOW or IRREGULAR rhythms:
Rate = Number of R waves X 6
The number of complexes (count R waves) on the rhythm strip gives the average rate
over a ten-second period. This is multiplied by 6 (10 seconds x 6 = 1 minute) to give
the average Beats per minute (bpm)

Fundamentals of ECG
Normal Heart Rate
What is the normal heart rate in adults?
Normal: 60–100 beats/min
Tachycardia: >100 beats/min
Bradycardia: <60 beats/min
What are the Normal Heart Rates in Children?
Newborn: 110 – 150 bpm
2 years: 85 – 125 bpm
4 years: 75 – 115 bpm
6 years+: 60 – 100 bpm

Fundamentals of ECG
What are the characteristics of Normal Sinus Rhythm (NSR)?
• The default heart rhythm.
• Pacemaking impulses arise from the sino-atrial node
and are transmitted to the ventricles via the AV-node
and His-Purkinje system.
• This results in a regular, narrow-complex heart rhythm
at 60-100 bpm.
• Each QRS complex is preceded by a normal P wave.
• Normal P wave axis: P waves should be upright in
leads I and II, inverted in aVR.
• The PR interval remains constant.
• QRS complexes are < 100 ms wide (unless a co-
existent interventricular conduction delay is present).

Fundamentals of ECG
What are the factors that can change heart rate?
• The sympathic system, e.g. epinephrine,
(=adrenalin) increases atrioventricular
conduction and contractility (the fight or
flight reaction.)
• The parasympathic system (nervus vagus,) e.g.
acetycholine, decreases the frequency and
atrioventricular conduction. The parasympathic
system affects mainly the atria.
• Cardiac filling increases the frequency.
• arrhythmias influence heart rate.

Fundamentals of ECG
What are the Variations on sinus rhythm?
• Sinus tachycardia = sinus rhythm with resting
heart rate > 100 bpm in adults, or above the
normal range for age in children.
• Sinus bradycardia= sinus rhythm with resting
heart rate < 60 bpm in adults, or below the
normal range for age in children.
• Sinus arrhythmia = sinus rhythm with a beat-to-
beat variation in the P-P interval (the time
between successive P waves), producing an
irregular ventricular rate.

Fundamentals of ECG
What are the Variations on sinus rhythm?
What is Sinus Arrhythmia ?
Sinus rhythm with a beat-to-beat variation in the P-P interval (the time
between successive P waves), producing an irregular ventricular rate.
What are the Characteristics of sinus arrhythmia?
•Variation in the P-P interval of more than 120 ms (3 small boxes).
•The P-P interval gradually lengthens and shortens in a cyclical
fashion, usually corresponding to the phases of the respiratory cycle.
•Normal sinus P wave with a constant morphology (i.e. no evidence of
premature atrial contractions).
•Constant P-R interval (i.e. no evidence of Mobitz I AV block).

Fundamentals of ECG
What are the Differential Diagnosis of sinus arrhythmia?
There are several other entities that cause
sinus rhythm with an irregular ventricular
rate:
 Frequent premature atrial contractions
 Second-degree AV block, Mobitz
I (Wenckebach phenomenon)
 Type I Sinoatrial Exit Block

Fundamentals of ECG
What is Sinus Bradycardia ?
• Sinus rhythm with a resting heart rate of < 60 bpm
in adults, or below the normal range for age in
children.
• A rhythm in which the rate of impulses arising from
the sinoatrial (SA) node is lower than expected.
• sinus bradycardia itself does not directly cause
symptoms, although a patient with comorbid
conditions that might be exacerbated by reduced
cardiac output (eg, angina, heart failure) may
present with worsening symptoms related to the
comorbidity.

Fundamentals of ECG
What is Sinus Bradycardia ?
• However, symptoms related to the slow heart rate can occur,
including fatigue, lightheadedness, presyncope or syncope,
and worsening of angina pectoris or heart failure.
• The aim of the initial evaluation is to establish the presence
or absence of symptoms, and any evidence of hemodynamic
compromise as a result of the bradycardia.
• Once hemodynamic compromise has been excluded, the
clinician will have to exclude diseases, cardiovascular or
other, associated with sinus bradycardia and, most
importantly, drugs associated with sinus bradycardia.

Fundamentals of ECG
What are the causes of Sinus Bradycardia ?
Non-pharmacological
 Normal during sleep
 Increased vagal tone (e.g. athletes)
 Vagal stimulation (e.g. pain)
 Inferior myocardial infarction
 Sinus node disease
 Hypothyroidism
 Hypothermia
 Anorexia nervosa
 Electrolyte abnormalities – hyperkalaemia,
hypermagnesaemia
 Brainstem herniation (the Cushing reflex)
 Myocarditis

Fundamentals of ECG
What are the causes of Sinus Bradycardia ?
Pharmacological
 Beta-blockers
 Calcium-channel blockers (verapamil & diltiazem)
 Digoxin
 Central alpha-2 agonists (clonidine &
dexmedetomidine)
 Amiodarone
 Opiates
 GABA-ergic agents (barbiturates,
benzodiazepines, baclofen, GHB)
 Organophosphate poisoning

Fundamentals of ECG
What is Sinus tachycardia?
• Sinus rhythm with a resting heart rate of > 100
bpm in adults, or above the normal range for age
in children.
• Sinus tachycardia is a rhythm in which the rate of
impulses arising from the sinoatrial (SA) node is
elevated.
• It is one of the most commonly encountered, and
often overlooked, rhythm disturbances that may
portend an adverse prognosis, particularly in
patients with cardiovascular disease.

Fundamentals of ECG
What are the causes of Sinus tachycardia?
 Exercise
 Pain, anxiety
 Hypoxia, hypercarbia
 Acidaemia
 Sepsis, pyrexia
 Pulmonary
embolism
 Hyperthyroidism
 Beta-agonists: adrenaline,
isoprenaline, salbutamol,
dobutamine
 Sympathomimetics: amph
etamines, cocaine,
methylphenidate
 Antimuscarinics: antihista
mines, TCAs,
carbamazepine, atropine
 Others: caffeine,
theophylline, marijuana
Non-pharmacological Pharmacological

Fundamentals of ECG
What is Inappropriate sinus tachycardia ?
• Inappropriate sinus tachycardia, also called chronic
nonparoxysmal sinus tachycardia, is an unusual condition
that occurs in individuals without apparent heart disease
or other cause for sinus tachycardia, such as
hyperthyroidism or fever, and is generally considered a
diagnosis of exclusion.
• Inappropriate sinus tachycardia is defined as a resting
heart rate >100 beats per minute (with a mean heart rate
>90 beats per minute over 24 hours) associated with
highly symptomatic palpitations .

Fundamentals of ECG
What are the diagnostic criteria of sinus tachycardia ?
• P wave axis and morphology similar or identical to sinus
rhythm.
• Resting heart rate of 100 beats per minute or greater
(with a mean heart rate >90 beats per minute over 24
hours) or with activity heart rates of 100 beats per minute
or greater but in excess of what one would expect for the
amount of exertion.
• Additionally, patients with inappropriate sinus tachycardia
classically experience a drop in heart rate during sleep.
• Palpitations, presyncope, or both related to the
tachycardia.
• Very rarely do patients experience syncope.

Fundamentals of ECG
What are the diagnostic criteria of sinus tachycardia ?
• Exclusion of identifiable causes of sinus tachycardia.
• Exclusion of atrial tachycardia.
• Most of these patients are young and female.
• Affected patients have an elevated resting heart
rate and/or an exaggerated heart rate response to
exercise that is out of proportion to the body's
physiological needs; many patients have both.
• This tachycardia is related to a primary sinus node
abnormality, characterized by a high intrinsic heart
rate, depressed efferent cardiovagal reflex, and
beta-adrenergic hypersensitivity .

Fundamentals of ECG
Case-1: A 45 years old
man presented with
chest discomfort on
exertion and occasional
palpitation for last 3
months. His pulse
76/min, BP-130/80 mm
Hg. He had the following
ECG.
This ECG showing-
• Regular rhythm at 75 bpm.
• Normal P wave morphology and axis (upright in I and II, inverted in aVR).
• Narrow QRS complexes (< 100 ms wide).
• Each P wave is followed by a QRS complex.
• The PR interval is constant. Impression: normal sinus rhythm

Fundamentals of ECG
A 48 years old lady
presented with weight
gain, leg edema, cold
intolerance and
generalized weakness
for last 6 months. Her
pulse 50/min, BP-150/85
mm Hg. She had the
following ECG.
This ECG showing-
• Regular rhythm at 50 bpm.
• Normal P wave morphology and axis (upright in I and II, inverted in aVR).
• Narrow QRS complexes (< 100 ms wide).
• Each P wave is followed by a QRS complex.
• The PR interval is constant. Impression: sinus bradycardia

Fundamentals of ECG
A 21 years old medical
student presented with
chest tightness, palpitations
and vomiting before his
professional examination.
His pulse 105/min, BP-
110/75 mm Hg. On
emergency department, he
had the following ECG.
This ECG showing-
Regular rhythm at 105 bpm.
Normal P wave morphology and axis (upright in I and II, inverted in aVR).
Narrow QRS complexes (< 100 ms wide).
Each P wave is followed by a QRS complex.
The PR interval is constant. Impression: sinus tachycardia

Fundamentals of ECG
A 14 years old boy presented with
occasional palpitations and chest
discomfort for last several months .
His pulse 105/min, BP-110/75 mm
Hg. On emergency department, he
had the following ECG.
This ECG showing-
• Normal sinus P waves (upright in leads I and II) with a constant morphology — albeit with
an appearance suggestive of left atrial enlargement.
• P-R interval is constant (no evidence of AV block).
• The P-P interval varies widely from 1.04 seconds (heart rate ~57 bpm) down to
0.60 seconds (heart rate ~100 bpm); a variability of over 400ms.
• For irregular rhythms such as this, the ventricular rate is best estimated by multiplying the
total number of complexes in the rhythm strip by 6. This gives an overall rate of 12 x 6 = 72
bpm.
Impression: sinus arrhythmia

Approach to a patient with Heart rate abnormality in ECG

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