Ep 138: A 67-Year-Old Male After ICD Firing

This episode covers implantable cardiac defibrillators and their management.

See more on this topic on AccessMedicine.

Transcript

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[Ms. Heidhausen] This is Katerina Heidhausen, executive editor of Harrison's Principles of Internal Medicine. Harrison's Podclass is brought to you by McGraw Hill's AccessMedicine, the online medical resource that delivers the latest content from the best minds in medicine. And now, on to the episode. 

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[Dr. Handy] Hi everyone, welcome back to Harrison's Podclass. We're your co-hosts. I'm Dr. Cathy Handy. 

[Dr. Wiener] And I'm Dr. Charlie Weiner and we're joining you from the Johns Hopkins School of Medicine. Welcome to episode 138: a 67-year-old after an ICD firing. Cathy, today's patient is a 67-year-old man who was diagnosed five years ago with cardiac sarcoid. The diagnosis was made by MRI and myocardial biopsy after he presented with symptomatic palpitations from ventricular tachycardia. 

[Dr. Handy] Okay, just to remind folks about sarcoidosis. It's a multi-system granulomatous inflammatory disease that typically involves the lungs, but also the joints, skin, and central nervous system. MRI and ultrasound allow for greater diagnostic accuracy, so more patients have been found to have cardiac sarcoidosis more recently. 

[Dr. Wiener] Yeah, and our patient's been treated with amiodarone and prednisone, and in addition, an implantable cardiac defibrillator was placed. At initial diagnosis, his systolic function was mildly impaired with an ejection fraction of 45%. A year ago, he was taken off his oral amiodarone because his cardiac function was improved, and his MRI showed improvement. 

[Dr. Handy] Patients with cardiac sarcoid may present with arrhythmias, such as ventricular tachycardia, or heart block, or cardiomyopathy. And many patients may present without concomitant lung findings, so your index of suspicion should be high in patients presenting with new or unexplained dysrhythmias or cardiomyopathies. 

[Dr. Wiener] Great. So our patient reports that his last ICD shock was three years ago until last night while celebrating his grandson's birthday. In retrospect, he did not recall any symptoms prior to the noticeable shock. After that, he was a bit shook but otherwise felt well. His spouse took his pulse after the shock, and it was 72, and his blood pressure was 125/75. He did not call you yesterday because of the birthday festivities. Our question is asking, in this patient, which of the following statements is true? Option A. is, antitachycardia pacing is typically ineffective before administering a shock. Option B. is, he should be restarted on amiodarone immediately. Option C. is, his cardiac function should be reassessed for worsening cardiomyopathy. Option D. is, patients find these shock episodes reassuring as they are definitive therapy. And option E. is, the patient absolutely should have contacted you immediately after the episode. 

[Dr. Handy] Okay, so we have some issues to discuss here. So just to summarize, we have a patient who has a history of ventricular tachycardia and defibrillation via ICD who had another episode. A substantial number of patients who receive an ICD can be expected to have an arrhythmia that is terminated by the ICD. Although this is an expected event, it's noteworthy because, for one, it can be a sign of impending instability. Two, it can signal deterioration of cardiac function, or it might mean the emergence of a new arrhythmia. For any of those, the patient requires evaluation. Interrogation of the ICD is crucial after a patient reports a shock or symptoms of arrhythmia to confirm that the therapy was indeed delivered for a ventricular arrhythmia and not for lead malfunction or an atrial arrhythmia. 

[Dr. Wiener] Okay, so it sounds like the answer is C. He needs a reevaluation for worsening cardiomyopathy. 

[Dr. Handy] Yes, that's the correct answer. And the decision about reinstituting anti-arrhythmic pharmacotherapy can wait for that evaluation and whether he has any additional episodes. 

[Dr. Wiener] Okay, so then option B. about the amiodarone is not true. What about option E? Shouldn't he have contacted you or someone immediately? 

[Dr. Handy] Well, that's a judgment call. After a shock, and in the absence of other symptoms to suggest arrhythmia or ischemia, patients have the option of waiting until the next working day or using remote monitoring to transmit device interrogation data to their physician. So in his case, he acted reasonably. However, the occurrence of multiple ICD shocks does warrant immediate medical attention, and patients should be told to never drive to the hospital themselves after receiving a shock from their ICD. 

[Dr. Wiener] That's good advice. Option D. mentions patient views of these attacks. Since we know that it is not the correct answer, I assume that patients do not find these reassuring. 

[Dr. Handy] Well, I'm sure it's reassuring at some level as the patient or family member to know that the ICD is preventing sudden death, but shocks reduce the quality of life and can lead to post-traumatic stress disorder. 

[Dr. Wiener] Which leads us to option A. Antitachycardia pacing. Tell me about that. 

[Dr. Handy] Modern ICDs have the capacity to terminate an arrhythmia episode with antitachycardia pacing or administration of a cardioversion shock. Studies have shown that antitachycardia pacing effectively terminates over 70% of VT episodes, even when the VT is very rapid. Most ICDs can be programmed to attempt overdrive pace termination during capacitor charge. If the arrhythmia then terminates, the shock is aborted. Appropriate programming of antitachycardia pacing is therefore critical for reducing shocks. For patients implanted with ICDs as primary prevention, programming of VF detection zones over 220 beats per minute significantly reduces unnecessary and inappropriate shocks. Long detection times will also help avoid unnecessary therapies for VT episodes liable to terminate spontaneously. 

[Dr. Wiener] Interesting. So the teaching points in this case are that implantable cardiac defibrillators or ICDs can be lifesaving for patients with recurrent episodes of VT or ventricular fibrillation and selected patients with cardiomyopathy. The triggering of an ICD should be followed by an interrogation of the device, and depending on those findings, an evaluation of cardiac function. ICDs may be programmed to avoid or lessen the frequency of administering a shock by utilizing antitachycardia pacing. Patients should be educated about how to proceed in the event of an ICD firing. 

[Dr. Handy] So this question and other questions like it can be found in Harrison's Self-Review, and you can read more about this topic in the Harrison's chapter on electrical storm. Visit the show notes for links to helpful resources, including related chapters and review questions from Harrison's, available exclusively on AccessMedicine. If you enjoyed this episode, please leave us a review, so we can reach more listeners just like you. Thanks so much for listening. 

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