Hypertrophic Cardiomyopathy

To the Editor: We feel compelled to object to much of the content of the article on hypertrophic cardiomyopathy (HCM) by Dr Fananapazir,¹ published as a Grand Rounds from the National Institutes of Health.

First, the ventricular septal myotomy-myectomy operation is at present the treatment of choice for patients with severe outflow obstruction and disabling symptoms refractory to drug treatment. At experienced centers, surgery has proved (for more than 40 years) to be highly successful in relieving obstruction and symptoms on a long-term basis and has an operative mortality that is now low (≤1%-2%).² Indeed, some surgeons have reported virtually no operative mortality in more recent years.³ Therefore, the statement by Fananapazir that "these are major operations with significant mortality and morbidity" is misleading. Readers should be aware that surgery remains an important option for severely symptomatic patients with obstructive HCM.

Second, the significance of dual-chamber pacing in the management of obstructive HCM is exaggerated. Initial enthusiasm for this treatment modality was based on observational and uncontrolled studies. More recent randomized studies and well-controlled investigations (not cited by Fananapazir) have demonstrated a strong placebo effect to be the predominant mechanism for perceived, short-term symptomatic improvement with pacing.^{4 - 6}

Third, for more than 25 years, echocardiography has been (and remains) the standard for the clinical diagnosis of HCM by virtue of characterizing the HCM phenotype (ie, otherwise unexplained left ventricular wall thickening in the absence of cavity dilatation).⁷ However, Fananapazir did not include 2-dimensional echocardiography among a list of the 8 most common tests customarily performed to diagnose and evaluate patients with HCM (Table 3 of his article). Also, Doppler echocardiography provides a reliable noninvasive measure of outflow gradient that eliminates the necessity of serial cardiac catheterizations in HCM. Therefore, Fananapazir's list of useful tests (which includes catheterization, but excludes echocardiography) may importantly mislead clinicians about diagnostic strategy and expose patients to unnecessary invasive procedures.

Fourth, the prognosis of HCM has been misrepresented. The author's discussion is confined to the most extreme unfavorable consequences of the disease and fails to provide a balanced accounting of this heterogeneous condition, in which many patients achieve normal life expectancy or experience only mild symptoms without major interventions.⁸ The clear inference provided by Fananapazir that virtually all HCM patients require electrophysiologic testing with programmed ventricular stimulation to assess their risk level for sudden death is an outdated concept that deviates substantially from current standard management and the views of experts in this field.

It is in the best interests of the patients with HCM and their clinicians that the portrayal of HCM and its management be accurate and free of personal bias and, indeed, take into account the broad scientific knowledge currently available regarding this condition. Half of Fananapazir's references are to his own work, which does not reflect the substantial literature in the field.