Which of the following is the most common condition associated with sudden cardiac death in the United States?
CAD. CAD is the predominant disease process associated with sudden cardiac death in the United States, accounting for 64% to 90% of cases. The other cardiomyopathies, such as dilated and hypertrophic cardiomyopathies, together account for approximately 10% to 15% of cases of sudden cardiac death.
A 55-year-old man is referred for recurrent syncope. The episodes consist of a prodrome of weakness and nausea followed by loss of consciousness. Physical examination is unremarkable. ECG and exercise treadmill stress test were normal.
Which of the following is the most appropriate next step?
Head-upright tilt-table testing. Syncope in the absence of structural heart disease is most likely neurally mediated (vasovagal). The head-upright tilttable test is the most appropriate test to evaluate for this condition. This test initiates the vasovagal episode by maximizing venous pooling, sympathetic activation, and circulating catecholamines. In general, the test involves at least 30 minutes of 70-degree head-up tilt angle without a saddle support. An addition of a catecholamine challenge with isoproterenol is sometimes used. Among symptomatic patients, the sensitivity of the head-upright tilttable test is approximately 85%. The specificity of the head-upright tilt-table test is good, with the frequency of an abnormal tilt-table test in control subjects being 0% to 15%. In the absence of structural heart disease, EP study, ambulatory Holter monitoring, and the signal-averaged ECG are low yield.
A 40-year-old woman presents to the emergency department with tachycardia. An ECG shows regular narrow complex tachycardia at 160 bpm. Atrial activity is difficult to discern in the tracing, but during tachycardia, there appears to be an “r'” in lead V1 that is not present on an ECG during sinus rhythm recorded a few months earlier.
Which of the following is the most likely diagnosis?
AVNRT. An “r'” in lead V1 during regular narrow complex tachycardia that is not present during sinus rhythm indicates the inscription of the P wave in the terminal QRS, is consistent with a very short VA interval, and is very specific for AVNRT.
An 80-year-old man with chronic AFib of 15 years’ duration is admitted with recurrent episodes of dizziness and a recent episode of syncope. He has normal LV function and no evidence of CAD. In-hospital telemetry confirms the presence of slow ventricular rate and frequent pauses (4 seconds) that correlate with his lightheadedness. His medications consist of warfarin sodium (Coumadin).
The most appropriate course of action includes which of the following?
Permanent pacemaker implant. This patient has evidence of symptomatic bradycardia on Holter monitoring, which constitutes a class I indication for permanent pacemaker placement. He has AV conduction system disease with no obvious reversible causes, which is most probably caused by idiopathic fibrosis (Lev disease). Prolonged monitoring will probably show more episodes of bradycardia, which was already seen during telemetry, and which places this elderly patient at risk for syncope and injury. EP testing for ventricular arrhythmia is not indicated in view of the absence of structural heart disease. Likewise, ICD is not indicated.
A decision was made in the previous case to proceed with a permanent pacemaker.
Which would be the most suitable pacing modality?
Single-chamber system in the ventricle programmed to VVIR. This patient is in chronic AFib, and, therefore, physiologic pacing in the atrium cannot be achieved. Furthermore, conversion and long-term maintenance of sinus rhythm in this situation are very unlikely. Therefore, there is no indication for placement of an atrial lead. DDDR with mode switching and DDIR will behave like a VVIR system in this patient, at the expense, however, of an additional lead (atrial) and a more expensive dual-chamber pacemaker.
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