A 75-year-old man has an active problem list, including coronary artery disease and myocardial infarction with both initial and repeat coronary artery bypass graft surgeries, cardiac arrest necessitating an implanted cardioverter defibrillator (ICD), chronic congestive heart failure with a left ventricular ejection fraction of 20%, chronic atrial fibrillation, hepatic cirrhosis with end-stage liver disease, and chronic renal failure. 

His problems also include a coagulopathy due to end-stage liver disease, grade 1 esophageal varices, chronic iron deficiency anemia, hypothyroidism, and hyperlipidemia. As expected, he is followed by a host of specialty services, including cardiology, hematology, nephrology, hepatology, and gastroenterology. 

His current medication list includes aspirin, folate, valsartan, isosorbide, furosemide, digoxin, carvedilol, atorvastatin, amiodarone, levothyroxine, spironolactone, nadolol, and esomeprazole. He is allergic to penicillin and cephalosporins. 

The man was once a heavy smoker and alcohol user but has abstained for the past five years. Family history is remarkable for coronary artery disease, hypertension, and aortic dissection. 

The review of systems is notable for a 20-lb weight loss over the past four months, generalized weakness with loss of muscle tone, and easy bruising. He has ascites that require drainage on a monthly basis. The patient denies gastrointestinal, neurologic, or pulmonary symptoms, and he has had no therapies from his ICD.

The ICD is a dual-chamber defibrillator. Pacing is programmed DDD at a lower rate of 60 beats/min and an upper rate of 120 beats/min. The paced AV delay is 150 ms, and the sensed AV delay is 120 ms. Ventricular fibrillation (VF) detection is programmed to detect at rates higher than 320 ms (188 beats/min), and all therapies are programmed to deliver 35 J. 

On physical examination, the man’s weight is 129 lb; blood pressure, 104/68 mm Hg; pulse, 66 beats/min; temperature, 35.9°C; respiratory rate, 16 breaths/min; and O2 saturation, 97% on room air. The patient is a thin, frail man in no apparent distress.

Pertinent physical findings include clear lungs bilaterally; a regular heart rate and rhythm with a grade II/VI systolic murmur and jugular venous distention to the jaw line, a protuberant abdomen with a fluid wave present, a liver edge palpable 4 cm below the right costal margin, and bilateral shoddy lymphadenopathy in both groins. Pitting edema is present on both lower extremities, and he has multiple ecchymoses on his arms, chest, and right leg. The patient is neurologically intact.

His ECG in clinic today includes the following:  a ventricular rate of 61 beats/min; PR interval, 464 ms; QRS duration, 192 ms; QT/QTc interval, 510/513 ms; R axis, 133°; and T axis, –34°. What is your interpretation of this ECG?

ANSWER

This patient’s ECG demonstrates an electronic ventricular pacemaker that is pacing at the lower programmed rate of 60 beats/min. All ICDs are able to provide pacing, cardioversion, and defibrillation. In DDD programmed pacing, four options are possible: atrial-sense/ventricular-sense, atrial-sense/ventricular-pace, atrial-pace/ventricular-sense, and atrial-pace/ventricular-pace.

In this case, atrial activity is sensed, and following an interval of 120 ms (programmable sensed AV delay), there is no spontaneous ventricular depolarization, so the ventricle is paced. Ventricular pacing at the right ventricular apex results in ventricular depolarization, which does not follow the typical His-Purkinje system. Hence, the paced morphology is wide, and repolarization (T wave) is abnormal as well. 

On this ECG, P waves are not discernible, so the PR interval measured by the computer is inaccurate. When the defibrillator is interrogated, intracardiac ECGs do show atrial activity, however, which confirms that the pacing function of the ICD is working appropriately. 

The purpose of this case presentation is to demonstrate the appearance of ventricular pacing.