Faculty Bibliography

The clinical use of the implantable cardioverter-defibrillator (ICD) is well established to prevent sudden death in patients with left ventricular dysfunction due to coronary artery disease and dilated cardiomyopathy, and its use has saved thousands of lives. More recently, its use has been extended to other patients at risk for sudden cardiac arrest due to ventricular fibrillation: patients with structural heart diseases such as hypertrophic cardiomyopathy and arrhythmogenic right ventricular dysplasia and patients with normal cardiac anatomy and function except for electrophysiologic abnormalities that predispose to cardiac arrest: Brugada syndrome and long QT syndrome. A distinguishing feature of these patients may be the young age when they present for either primary or secondary prevention. This contrasts with the "first wave" of adult ICD implantations that were usually performed in elderly or middle aged patients. An important consideration in favor of ICD implantation in young patients with sudden death risk is the long and cumulative period of their risk. Similarly, after implantation, these patients will experience the long-term risks of ICD implantation. This review focuses on the unique challenges presented by device implantation in young patients 16 to 45 years of age who may have 4 to 7 decades of life with their devices. Although devices may prolong life, they come with problems that will pose unique challenges for both patients and their physicians. Moreover, because of the long durations, these problems may accelerate as patients age.

When severe COPD and obstructive hypertrophic cardiomyopathy (HCM) coexist, management is challenging and complex. Drug contraindications limit pharmacologic options. Patients may not be candidates for surgical septal myectomy due to severe pulmonary disease. We describe a case of an elderly woman with severe reactive COPD who presented with an infectious exacerbation and dyspnea that progressed to near intubation due to heart failure from coexistent obstructive HCM. Transthoracic echocardiography revealed massive asymmetric septal hypertrophy and a diffusely hyperkinetic left ventricle with a left ventricular outflow tract (LVOT) gradient of 92 mm Hg. Two and a half hours after oral administration of disopyramide, LVOT gradient had decreased to 25 mm Hg with a corresponding immediate improvement in symptoms.

CONTEXT: Recently, the implantable cardioverter-defibrillator (ICD) has been promoted for prevention of sudden death in hypertrophic cardiomyopathy (HCM). However, the effectiveness and appropriate selection of patients for this therapy is incompletely resolved. OBJECTIVE: To study the relationship between clinical risk profile and incidence and efficacy of ICD intervention in HCM. DESIGN, SETTING, AND PATIENTS: Multicenter registry study of ICDs implanted between 1986 and 2003 in 506 unrelated patients with HCM. Patients were judged to be at high risk for sudden death; had received ICDs; underwent evaluation at 42 referral and nonreferral institutions in the United States, Europe, and Australia; and had a mean follow-up of 3.7 (SD, 2.8) years. Measured risk factors for sudden death included family history of sudden death, massive left ventricular hypertrophy, nonsustained ventricular tachycardia on Holter monitoring, and unexplained prior syncope. MAIN OUTCOME MEASURE: Appropriate ICD intervention terminating ventricular tachycardia or fibrillation. RESULTS: The 506 patients were predominately young (mean age, 42 [SD, 17] years) at implantation, and most (439 [87%]) had no or only mildly limiting symptoms. ICD interventions appropriately terminated ventricular tachycardia/fibrillation in 103 patients (20%). Intervention rates were 10.6% per year for secondary prevention after cardiac arrest (5-year cumulative probability, 39% [SD, 5%]), and 3.6% per year for primary prevention (5-year probability, 17% [SD, 2%]). Time to first appropriate discharge was up to 10 years, with a 27% (SD, 7%) probability 5 years or more after implantation. For primary prevention, 18 of the 51 patients with appropriate ICD interventions (35%) had undergone implantation for only a single risk factor; likelihood of appropriate discharge was similar in patients with 1, 2, or 3 or more risk markers (3.83, 2.65, and 4.82 per 100 person-years, respectively; P = .77). The single sudden death due to an arrhythmia (in the absence of advanced heart failure) resulted from ICD malfunction. ICD complications included inappropriate shocks in 136 patients (27%). CONCLUSIONS: In a high-risk HCM cohort, ICD interventions for life-threatening ventricular tachyarrhythmias were frequent and highly effective in restoring normal rhythm. An important proportion of ICD discharges occurred in primary prevention patients who had undergone implantation for a single risk factor. Therefore, a single marker of high risk for sudden death may be sufficient to justify consideration for prophylactic defibrillator implantation in selected patients with HCM.

OBJECTIVES: We investigated the cause of the midsystolic drop (MSD) in left ventricular (LV) ejection velocities that are observed with hypertrophic cardiomyopathy (HCM) and severe obstruction. BACKGROUND: Dynamic obstruction is an important determinant of symptoms and adverse outcome. The MSD in velocity and flow occurs in patients with gradients >60 mm Hg. The nadir velocity in the LV occurs simultaneously with peak gradient. METHODS: We studied 36 patients with obstructive HCM and an MSD and compared them with 15 patients with HCM and no obstruction and with 25 age-matched normal control subjects. We measured LV ejection velocity proximal and distal to LV obstruction as well as tissue Doppler velocities and time intervals. RESULTS: The duration of contraction of both the septum and lateral wall is shorter in obstructed patients with the MSD than in nonobstructed HCM patients: septal contraction 203 +/- 68 ms vs. 271 +/- 41 ms (p < 0.001). Parallel reduction in the length of shortening was noted: 1.2 +/- 0.6 cm vs. 1.9 +/- 0.4 cm (p < 0.001). The ejection velocity nadir follows the septal and lateral peak velocities by 100 ms and 60 ms, respectively. The velocity nadir occurs as both walls rapidly decelerate to their premature termination: septal deceleration 79 +/- 35 cm/s2 vs. 48 +/- 21 cm/s2 (p < 0.001). With medical abolition of obstruction the MSD disappears and the duration and length of contraction normalizes. CONCLUSIONS: These data indicate that the MSD is caused by premature termination of LV segmental shortening and is a manifestation of systolic dysfunction.

Hypertrophic cardiomyopathy (HCM) is a heterogeneous disease of cardiac muscle which can present with myriad functional and clinical manifestations. When symptoms and left ventricular outflow gradients are present, it is primarily treated with pharmacologic agents. For refractory patients, dual chamber pacing has been proposed; by altering timing and site of cardiac electrical activation, the hemodynamic abnormalities in HCM may be modified. Results of non-randomized and randomized trials have shown an average gradient reduction of 50%. However, pressure gradient reduction within the left ventricular outflow tract (LVOT) has not translated into improved objective functional measurements, even though subjective parameters may improve. Dual chamber pacing cannot be recommended as primary treatment for obstruction except in a subset of patients who are elderly or have significant comorbidities that preclude surgery. However, many patients will now receive implantable cardioverter-defibrillators (ICD) which will include both right atrial and right ventricular leads. This will allow DDD pacing which may be utilized for symptom palliation. Future investigations will determine if alternate forms of pacing, including left atrial or left ventricular pacing, may improve objective measures in these patients.