Characteristics of hypertrophic obstructive cardiomyopathy refractory to medical treatment and selection of surgical methods

BACKGROUND AND AIM OF THE STUDY: Treatment for hypertrophic obstructive cardiomyopathy (HOCM) has been reported; however, there has been no report on the characteristics of medication-responsive and -refractory hypertrophic obstructive cardiomyopathy (HOCM). Using the classification of systolic anterior movement (SAM) which has been previously reported, we tried to identify the characteristics and use them to treat HOCM appropriately. METHODS: The clinical, echocardiographic, catheterization, and surgical data of 29 hospitalized patients with HOCM during 1980 to 1999 were analyzed retrospectively. We classified SAM in all patients by echocardiography. Nineteen patients improved with medical treatment (medical group), and 10 patients underwent surgical treatment because of ineffectiveness of medication (surgical group). We studied the relation between types of SAM and medical/surgical groups, and examined the relation between types of SAM and the surgical methods. RESULTS: Type I SAM was significantly more frequent in the medical group, while type II SAM was more frequent in the surgical group (p = 0.047). Patients in the surgical group underwent mitral valve replacement (MVR), myectomy, or a combination of MVR and myectomy. Left ventricular outflow gradient (LVOG) of over 100 mmHg was recognized in almost all patients with type II SAM. CONCLUSIONS: It was suggested that patients with medication-responsive HOCM tended to have type I SAM and those with refractory HOCM tended to have type II SAM. We consider that in type I SAM, if the position of the papillary muscles changed with medication or myectomy, shift of the chordae and type I SAM were reduced or disappeared. However, in type II SAM, even if the position of the papillary muscles changed, SAM did not disappear because lifting of the mitral leaflets remained. It is therefore suggested that patients with type II SAM should undergo at least MVR.