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Emergency cardiac pacing

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transvenous and transcutaneous pacing

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Emergency cardiac pacing

  1. 1. Emergency Cardiac Pacing
  2. 2. • Emergency cardiac pacing may be instituted either prophylactically or therapeutically. • Prophylactic indications include patients with a high risk for AV block. • Therapeutic indications include symptomatic bradyarrhythmias and overdrive pacing. • Transcutaneous and transvenous are the two techniques most commonly used in the ED.
  3. 3. • Because it can be instituted quickly and noninvasively, transcutaneous pacing is the technique of choice in the ED when time is of the essence. • Transvenous pacing should be reserved for patients who require prolonged pacing or have a very high (>30%) risk for heart block.
  4. 4. EMERGENCY TRANSVENOUS CARDIAC PACING • The technique can be performed in less than 20 minutes in 72% of patients and in less than 5 minutes in 30%. • Transcutaneous cardiac pacing (TCP) has become the mainstay of emergency cardiac pacing and is often used pending placement of a transvenous catheter or to determine whether potentially terminal bradyasystolic rhythms will respond to pacing.
  5. 5. Bradycardias  Sinus Node Dysfunction: • may be manifested as sinus arrest,sick sinus syndrome or sinus bradycardia • is a common indication for elective permanent pacing, it is seldom cause for emergency pacemaker insertion. • 17% percent of patients with acute myocardial infarction (AMI) will experience sinus bradycardia. (occurs more frequently with inferior > anterior infarction) • Sinus node dysfunction frequently responds to medical therapy but requires prompt pacing if such therapy fails.
  6. 6. Bradycardias  Asystolic Arrest: • Transvenous pacing in an asystolic or bradyasystolic patient has little value and is not recommended • Failure of effective pacing is primarily related to the state of the myocardial tissue. • Cardiac pacing may be used as a “last-ditch” effort in bradyasystolic patients but is rarely successful and is not considered standard practice. • Given the continued emphasis on the importance of maximizing chest compressions during CPR, interrupting CPR to institute emergency pacing is not recommended
  7. 7. Bradycardias  AV Block: • In symptomatic patients without myocardial infarction (MI) and in asymptomatic patients with a ventricular rate lower than 40 beats/min, pacemaker therapy is indicated. • AV block occurring during anterior infarction is believed to result from diffuse ischemia in the septum and infranodal conduction tissue. • Because these patients tend to progress to high-degree block without warning, a pacemaker is often placed prophylactically • A hemodynamically unstable patient who is unresponsive to medical therapy should be paced promptly.
  8. 8. Bundle Branch Block and Ischemia  Bundle branch block occurring in AMI is associated with a higher mortality rate and a greater incidence of third degree heart block than is uncomplicated infarction.  Because of the increased risk, consider pacing for the following conduction blocks:  New-onset LBBB  RBBB with left axis deviation or other bifascicular block  Alternating bundle-branch block
  9. 9. Tachycardias  Hemodynamically compromising tachycardias are usually treated by medical means or electrical cardioversion  Supraventricular dysrhythmias,with the exception of AF, respond well to atrial pacing.  By “overdrive” pacing the atria at rates 10 to 20 beats/min faster than the underlying rhythm, the atria become entrained, and when the rate is slowed, the rhythm frequently returns to normal sinus.  Overdrive pacing is especially useful for arrhythmias with recurrent prolonged QT intervals such as those seen with quinidine toxicity or torsades de pointes  Transvenous pacing is also useful in patients with digitalis-induced dysrhythmias, in whom direct current cardioversion may be dangerous
  10. 10. Cardiac Pacing for Drug-Induced Dysrhythmias  Tachycardic rhythms from amphetamines, cocaine, anticholinergics, cyclic antidepressants,theophylline, and other drugs do not benefit from cardiac pacing  Severe bradycardia and heart block often accompany overdose of digitalis preparations, β-adrenergic blockers, and CCB  Cardiac pacing is not generally effective for serious toxin- induced bradycardias
  11. 11. Contraindications  The presence of a prosthetic tricuspid valve is generally considered to be an absolute contraindication to transvenous cardiac pacing  Severe hypothermia will occasionally result in ventricular fibrillation when pacing is attempted  Rapid and careful rewarming is often recommended first, followed by pacing if the patient’s condition does not improve.
  12. 12. Pacing Generator  An amperage control allows the operator to vary the amount of electrical current delivered to the myocardium, usually 0.1 to 20 mA  increase the output improves the likelihood of capture  By increasing the sensitivity, one can convert the unit from a fixed-rate (asynchronous mode) to a demand (synchronous mode) pacemaker  The typical pacing generator has a sensitivity setting that ranges from about 0.5 to 20 mV  Decreasing the setting increases the sensitivity and improves the likelihood of sensing myocardial depolarization  In the fixed-rate mode ,the unit does not sense any intrinsic electrical activity  In the full-demand mode, however, the pacemaker senses the underlying ventricular depolarizations, and the unit does not fire as long as the patient’s ventricular rate is equal to or faster than the set rate of the pacing generator
  13. 13. Pacing Generator
  14. 14. Pacing Catheters and Electrodes  Pacing catheters, most range from 3 to 5 Fr in size and are approximately 100 cm in length.  For emergency pacing, the semifloating bipolar electrode catheter with a balloon tip is used most frequently  Before insertion, the balloon is checked for leakage of air by inflating and immersing it in sterile water.  An inflated balloon helps the catheter “float” into the heart, even in low-flow states, but is obviously not advantageous in the cardiac arrest situation  All pacemaker systems must have both a positive (anode) and a negative (cathode) electrode
  15. 15. Pacing Catheters and Electrodes  In the typical bipolar catheter used for temporary transvenous pacing, the cathode (stimulating electrode) is at the tip of the pacing catheter  The anode is located 1 to 2 cm proximal to the tip, and a balloon or an insulated wire separates the two electrodes.  With a bipolar catheter, the cathode does not need to be in direct contact with the endocardium for pacing to occur, although it is preferable to have direct contact.  In a unipolar system, the cathode is at the tip of the pacing catheter and the anode is located in one of three places: in the pacing generator itself, more proximally on the catheter (outside the ventricle), or on the patient’s chest.
  16. 16. Pacing Catheters and Electrodes
  17. 17. ECG Machine
  18. 18. Introducer Sheath  The introducer set is used to enhance passage of the pacing catheter through the skin, subcutaneous tissue, and vessel wall.  The size of the pacing catheter refers to its outside diameter, whereas the size of the introducer refers to its inside diameter. Thus, a 5-Fr pacing catheter will fit through a 5-Fr introducer.
  19. 19. Site Selection • The four venous channels that provide easy access to the right ventricle are the brachial, subclavian, femoral, and internal jugular veins • The right internal jugular and left subclavian veins have the straightest anatomic pathway to the RV and are generally preferred for temporary transvenous pacing • For subclavian,the infraclavicular approach is most commonly reported for all temporary transvenous pacemaker insertions • This route is preferred because of its easy accessibility, close proximity to the heart, and ease in catheter maintenance and stability
  20. 20. Site Selection
  21. 21. Site Selection
  22. 22. Skin Preparation and Venous Access • Clean the skin over the venipuncture site twice with an antiseptic solution such as chlorhexidine or povidone-iodine • An existing central venous pressure (CVP) line can be used to place the pacing catheter if the lumen of the catheter is large enough to accept a guidewire. • Withdraw the CVP line 3 to 5 cm to expose an area of sterile tubing. • Transect the tubing through a sterile area while holding it firmly at skin level. • Pass a guidewire through the tubing, and then withdraw the tubing so that only the wire is left in the vein
  23. 23. Pacemaker Placement • Connect the patient to the limb leads of an ECG machine, and turn the indicator to record the chest (V) lead • The distal terminal of the pacing catheter (the cathode or lead marked “negative”,“−.” or “distal”) must be connected to the V lead of the ECG machine • The ECG tracing recorded from the electrode tip localizes the position of the tip of the pacing electrode. • If a balloon-tipped catheter is used, inflate the balloon with air after the catheter enters the superior vena cava (≈10 to 12 cm for a subclavian or internal jugular insertion)
  24. 24. Pacemaker Placement • The sum of the electrical forces will be negative if the depolarization is moving away from the catheter tip and positive if the depolarization is moving toward the catheter tip. • if the tip of the catheter is above the atrium, both the P wave and QRS complex will be negative (i.e., the electrical forces of a normally beating heart will be moving away from the catheter tip). • As the tip progresses inferiorly in the atrium, the P wave will become isoelectric (biphasic) and will eventually become positive as the wave of atrial depolarization advances toward the tip of the catheter • Once the pacing catheter is in the desired position, deflate the balloon by unlocking the port, observing that the syringe refills with air spontaneously, and then removing the syringe
  25. 25. Pacemaker Placement • At the high right atrial level, both the P wave and QRS complex are negative. The P wave is larger than the QRS complex and is deeply inverted (see Fig. 15-6C and D). As the center of the atrium is approached, the P wave becomes larger and biphasic (see Fig. 15– 6E). As the catheter approaches the lower atrium (see Fig. 15-6F), the P wave becomes smaller and upright. The QRS complex is fairly normal. When striking the right atrial wall, an injury pattern with a P-Ta segment is seen (Fig. 15-6G). As the electrode passes through the tricuspid valve, the P wave becomes smaller and the QRS complex becomes larger (see Fig. 15-6H). Placement in the inferior vena cava may be recognized by a change in the morphology of the P wave and a decrease in the amplitude of both the P wave and the QRS complex
  26. 26. Pacemaker Placement • One should avoid drawing back on the syringe because this may rupture the balloon • If the syringe does not refill spontaneously, the operator should suspect that the balloon might be ruptured. • After successful passage of the catheter into the right ventricle,advance the tip until contact is made with the endocardial wall. When this occurs, the QRS segment will show ST-segment elevation • If the pacer enters the pulmonary artery outflow tract,the P wave again becomes negative, and the QRS amplitude diminishes • Once ventricular endocardial contact is made, disconnect the catheter from the ECG machine and connect the distal lead to the negative terminal on the pacing generator
  27. 27. Pacemaker Placement • Set the pacing generator at a rate of 80 beats/min or 10 beats/min faster than the underlying ventricular rhythm • Select the full-demand mode with an output of about 5 mA • Assess the patient for electrical and mechanical capture:  Electrical capture will be manifested on the ECG monitor as a pacer spike followed by a QRS complex  Mechanical capture means that a pacer spike with its corresponding QRS triggers a myocardial contraction • If complete capture does not occur or if it is intermittent, the pacer will need to be repositioned
  28. 28. Catheter Placement in Low-Flow States • If cardiac output is too low to “float” a pacing catheter or if the patient is in extremis, there may not be enough time to advance a pacing catheter via the previously described techniques • In such emergency situations, connect the pacing catheter to the energy source, turn the output to the maximum amperage, and select the asynchronous mode. • Advance the catheter blindly in the hope that it will enter the right ventricle and pacing will be accomplished
  29. 29. Testing Threshold • The threshold is the minimum current necessary to obtain capture. Ideally, it is less than 1.0 mA, and usually it is between 0.3 and 0.7 mA • To determine the threshold, set the pacing generator to maximum sensitivity (full-demand mode) at 5-mA output and a rate of approximately 80 beats/min (or at least 10 beats/min greater than the patient’s intrinsic rate • Reduce the current (output) slowly until capture is lost. This current is the threshold • Increase the amperage to 2.5 times the threshold to ensure consistency of capture (usually between 2 and 3 mA).
  30. 30. Testing Sensing • Set the rate at about 10 beats/min greater than the endogenous rhythm, place the pacemaker in asynchronous mode (minimum sensitivity, which is the maximum setting on the sensitivity voltage control), and ensure that there is complete capture • Then adjust the sensitivity control to its midposition or approximately 3 mV, and gradually decrease the rate until pacing is suppressed by the patient’s intrinsic rhythm. • The sensing indicator on the pacing generator should signal each time that a native beat is sensed and should be in synchrony with each QRS complex on the ECG monitor. • If the pacer fails to sense the intrinsic rhythm,increase the sensitivity (decrease the millivolts) until the pacer is suppressed • Conversely, if the sensing indicator is triggered by P or T waves or by artifact, decrease the sensitivity until only the QRS complex is sensed
  31. 31. Final Assessment • Assess pacemaker function again, and take a chest film to ensure proper positioning. Ideal positioning of the pacing catheter is at the apex of the right ventricle • A 12-lead ECG tracing should be obtained after placement of the transvenous pacemaker. If the catheter is within the right ventricle, a left bundle branch pattern with left axis deviation should be evident in paced beats • If an RBBB pattern is noted, coronary sinus placement or left ventricular pacing secondary to septal penetration should be suspected. • When the pacemaker achieves ventricular capture, there may be times when the atria contract against a closed tricuspid valve and a cannon wave results
  32. 32. Final Assessment
  33. 33. Complications • Therapy for catheter-induced ectopy during insertion involves repositioning the catheter in the ventricle. This usually stops the ectopy • if after repeated attempts it is found that the catheter cannot be passed without ectopy,myocardial suppressant therapy may be used to desensitize the myocardium. • Perforation of the ventricle is a well-described complication that can result in loss of capture
  34. 34. Complications • two-dimensional echocardiogram usually demonstrates the catheter’s extracardiac position. • Simply pulling the catheter back and repositioning it in the right ventricle can usually treat uncomplicated perforation. • During insertion of a temporary pacing catheter when a nonfunctioning permanent catheter is in place, there is a small risk of entanglement or knotting. • This potential also exists with other central lines and PACs. Even without the presence of other lines, the pacing catheter can become knotted.
  35. 35. Complications
  36. 36. Complications
  37. 37. TRANSCUTANEOUS CARDIAC PACING • may be preferable to transvenous pacing in patients who have received thrombolytic agents or other anticoagulants • Although small pediatric electrodes for TCP have been developed, experience with pediatric TCP has been limited • TCP is indicated for the treatment of hemodynamically significant bradydysrhythmias that have not responded to medical therapy • Hemodynamically significant implies hypotension, anginal chest pain, pulmonary edema, or evidence of decreased cerebral perfusion
  38. 38. TRANSCUTANEOUS CARDIAC PACING • This technique is temporary and is indicated for short intervals as a bridge until transvenous pacing can be initiated or the underlying cause of the bradydysrhythmia (e.g., hyperkalemia,drug overdose) can be reversed. • Though generally unsuccessful, TCP may be attempted for the treatment of asystolic cardiac arrest. In this setting the technique is efficacious only if used early after the onset of arrest (usually within 10 minutes). • All transcutaneous pacemakers have similar basic features.Most allow operation in either a fixed rate (asynchronous) or a demand mode (VVI).
  39. 39. Pad Placement • Take care to avoid placing the electrodes over an implanted pacemaker or defibrillator. • Remove any transdermal drug delivery patches if they are in the way. • Remove excessive hair if time permits • Place the anterior electrode (cathode or negative electrode) as close as possible to the point of maximal impulse on the left anterior chest wall • Place the second electrode directly posterior to the anterior electrode • On females, place the electrode beneath the breast and against the chest wall.
  40. 40. Pad Placement • Although the polarity of the electrodes does not appear to be important for defibrillation, at least one study has indicated that it may important be for pacing. • There is little risk for electrical injury to health care providers during TCP. The power delivered during each impulse is less than 1/1000 of that delivered during defibrillation • Inadvertent contact with the active pacing surface results in only a mild shock.
  41. 41. Pacing Bradycardiac Rhythms • Slowly increase the output from minimal settings until capture is achieved • Generally, a heart rate of 60 to 70 beats/min will maintain adequate blood pressure • Assess electrical capture by monitoring the ECG tracing • Assess mechanical capture by palpating the pulse • Because of muscular contractions triggered by the pacer, carotid pulses may be difficult to assess, so palpating the femoral pulse may be easier • Failure to capture with TCP may be related to electrode placement or patient size. Patients with barrel-shaped chests and large amounts of intrathoracic air conduct electricity poorly and may prove refractory to capture
  42. 42. Pacing Bradycardiac Rhythms • Patients who are conscious or who regain consciousness during TCP will experience discomfort because of muscle contraction. • Analgesia with incremental doses of an opioid agent, sedation with a benzodiazepine compound, or both, will make this discomfort tolerable until transvenous pacing can be instituted
  43. 43. Overdrive Pacing • Overdrive pacing of ventricular tachycardia or PSVT is performed in patients who are stable enough to tolerate the brief delay associated with the preparation needed for this technique • Set the pacer rate at approximately 20 to 60 pulses/min greater than the dysrhythmia rate • Generally, an impulse rate of 200 pulses/min is used for ventricular tachycardias and a rate of 240 to 280 pulses/ min is used for PSVT .
  44. 44. Complications • The major potential complication of TCP is failure to recognize the presence of underlying treatable ventricular fibrillation. This complication is primarily due to the size of the pacing artifact on the ECG screen • A rare complication of TCP is induction of ventricular Fibrillation. longer impulse durations used in modern devices seem to decrease the chance of inducing ventricular fibrillation

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