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Role of Hypertrophy in Sudden Death in
Hypertrophic Cardiomyopathy

Paolo Spirito, MD; Marco Piccininno, MD

Divisione di Cardiologia, Ente Ospedaliero Ospedali Galliera, Genoa, Italy

   Since the initial description of hypertrophic cardiomyopathy, more than 40 years ago, sudden cardiac death has been regarded as the most devastating and unpredictable feature of the natural history of the disease (1-3). This dramatic event remains the most common modality of death in children and young patients (4), and is most frequently caused by ventricular tachyarrhythmias (5).

CLINICAL INDICATORS OF RISK OF SUDDEN DEATH
   Despite intense investigation, risk stratification has been frustrated by certain features of hypertrophic cardiomyopathy: relatively low disease prevalence (6,7), extremely heterogeneous clinical course and prognosis (1-3), frequent absence of symptoms prior to sudden death (1-3), and the difficulty of enrolling large study populations not influenced by tertiary referral bias (8). Nevertheless, certain patient subgroups are generally considered at high risk of sudden death. Young patients who have survived a cardiac arrest with documented ventricular fibrillation and those who have had one or more episodes of sustained ventricular tachycardia are at high risk of experiencing a catastrophic event in the near future (1-3). A malignant family history of sudden death at young age (< 50 years), defined as two or more sudden deaths in primary related family members, is also considered to be an indicator of high risk (1-3) (Figure 1).

Figure 1

   A number of studies performed in tertiary referral centers have identified several additional variables that appear to confer an increased risk for sudden death, including non-sustained ventricular tachycardia on ambulatory electrocardiographic monitoring and exercise induced systemic arterial hypotension (3). These variables, however, have a low-positive predictive accuracy.

PROGNOSTIC VALUE OF LEFT VENTRICULAR HYPERTROPHY
   Extreme hypertrophy (defined as a maximal left ventricular wall thickness of 30 mm or more in adults and the equivalent corrected for body surface area in children) is part of the morphologic spectrum of hypertrophic cardiomyopathy. However, such a phenotypic expression of the disease is rarely encountered in patients older than 50, suggesting that most patients with extreme hypertrophy die prematurely (9,10,11) (Figure 2). On this basis, two recent studies have investigated the relation between magnitude of left ventricular hypertrophy and survival in two large and independent populations of patients with hypertrophic cardiomyopathy (12,13).

Figure 2

   The results of these studies have shown that maximal left ventricular wall thickness is an important marker of risk in this disease (Figure 3). Patients at the low end of the morphologic spectrum of the disease (< 20 mm wall thickness), in the absence of other generally accepted risk factors such as a family history of sudden death, recurrent nonsustained ventricular tachycardia on Holter, abnormal blood pressure response during exercise, recurrent syncope, or evolution to end-stage disease, were at low risk (10,12,13). Patients with higher degrees of hypertrophy showed a progressive increase of risk in relation to their wall thickness, and those with extreme hypertrophy (> 30 mm wall thickness) were at substantial long-term risk of sudden death, close to 20% at ten years and 40% at twenty years (Figure 4). In these latter patients, the coexistence of additional risk factors confers a high-risk profile and justifies aggressive intervention for prevention of sudden death. Adolescent and young patients with extreme hypertrophy appeared to have the highest rate of sudden death and may have an unfavorable prognosis also in the absence of additional risk factors. In such patients, management decision are complex and must take into account a number of issues. Even a relatively long-term risk of sudden death still has the likelihood of shortening considerably the life of a young patient. In addition, because most of these patients do not have symptoms of heart failure and/or systolic dysfunction at the time of sudden death (4), by preventing this mode of death we may perhaps be offering to some of these youths a normal life-span. These considerations suggest that we should inform explicitly these young patients with extreme hypertrophy and their families regarding the present uncertainties in risk stratification, as well as the life-saving capabilities and potential complications of the implantable defibrillator.

Figure 3

Figure 4

REFERENCES

1. Maron BJ, Bonow RO, Cannon RO III et al. Hypertrophic cardiomyopathy: interrelations of clinical manifestations, pathophysiology, and therapy. N Engl J Med 1987;316:780-9, and 844-52.

2. Wigle ED, Rakowski H, Kimball BP, Williams WG. Hypertrophic cardiomyopathy. Clinical spectrum and treatment. Circulation 1995;92:1680-92.

3. Spirito P, Seidman CE, McKenna WJ, Maron BJ. The management of hypertrophic cardiomyopathy. N Engl J Med 1997;336:775-85.

4. Maron BJ, Olivotto I, Spirito P et al. Epidemiology of hypertrophic cardiomyopathy-related death revisited in a large non-referral-based patient population. Circulation 2000;102:858-64.

5. Maron BJ, Shen WK, Link MS et al. Efficacy of the implantable cardioverter-defibrillator for the prevention of sudden death in hypertrophic cardiomyopathy. N Engl J Med 2000;342:365-73.

6. Maron BJ, Gardin JM, Flack JM et al. Prevalence of hypertrophic cardiomyopathy in a general population of young adults: echocardiographic analysis of 4111 subjects in the CARDIA Study. Circulation 1995;92:785-9.

7. Corrado D, Basso C, Schiavon M, Thiene G. Screening for hypertrophic cardiomyopathy in young athletes. N Engl J Med 1998;339:364-369.

8. Spirito P, Chiarella F, Carratino L et al. Clinical course and prognosis of hypertrophic cardiomyopathy in an outpatient population. N Engl J Med 1989;320:749-55.

9. Louie EK, Maron BJ. Hypertrophic cardiomyopathy with extreme increase in left ventricular wall thickness: functional and morphologic features and clinical significance. J Am Coll Cardiol 1986;8:57-65.

10. Spirito P, Maron BJ. Relation between extent of left ventricular hypertrophy and age in hypertrophic cardiomyopathy. J Am Coll Cardiol 1989;13:820-3.

11. Maron BJ, Piccininno M, Bernabò P et al. Extreme left ventricular hypertrophy is not compatible with advanced age in hypertrophic cardiomyopathy. Circulation 2000, 102, 18 Suppl II, 420 (abstract).

12. Spirito P, Bellone P, Harris KM et al. Magnitude of left ventricular hypertrophy and risk of sudden death in hypertrophic cardiomyopathy. N Engl J Med 2000;342:1778-85.

13. Elliot PM, Polonekki J Dickie S, et al. Sudden death in hypertrophic cardiomyopathy: identification of high risk patients. J Am Coll Cardiol 2000;36:2212-18.

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2nd Virtual Congress of Cardiology

Dr. Florencio Garófalo
Steering Committee
President
Dr. Raúl Bretal
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Technical Committee - CETIFAC
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