Prognosis
In the majority of cases, hypertrophic cardiomyopathy (HCM) carries a benign prognosis. At presentation 90% of patients will be asymptomatic, and the majority of those will remain asymptomatic on long-term follow-up. In one prospective study, the onset of any symptom was delayed until the patient was 70 years or older in 18% of patients.[10] Patients presenting with mild to moderate symptoms typically experience slow progression of symptoms with advancing age.
A subgroup of patients (5% of all HCM patients and 30% of tertiary referral populations) will develop symptomatic outflow tract obstruction that is refractory to medical therapy. Patients with resting provocable left ventricular (LV) outflow gradients >50 mmHg and severe limiting symptoms are candidates for surgical or catheter intervention.[2]
In patients who are asymptomatic at presentation, the annual mortality rate is lower than in those patients with symptoms (0.9% vs. 1.9%). Similarly, the annual rate of sudden death is lower in patients without symptoms at presentation (0.1% vs. 1.4%).[107] See Diagnostic approach for information about risk factors for sudden death.
The annual mortality rate for those patients diagnosed in childhood is substantially greater than that of the general population (1.3% vs. 0.08%). In contrast, the annual mortality rate for those diagnosed in adulthood is not significantly increased above the general population (2.2% vs. 1.9%).[108]
End-stage heart failure develops in around 2% to 15% of people with HCM and carries a poor prognosis.[109] Systolic function deteriorates, and the left ventricle remodels and becomes dilated. The mechanism of end-stage HCM is likely diffuse ischemic injury. Risk factors for end-stage disease include younger age at diagnosis, more severe symptoms, larger LV cavity size, and family history of end-stage disease. Mortality is high once symptomatic heart failure develops, with mean time to death or cardiac transplantation of 2.7 ± 2.1 years.[100]
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