Late benefits of dual-chamber pacing in obstructive hypertrophic cardiomyopathy: a 10-year follow-up study.

OBJECTIVE: To examine the mid-term and long-term outcomes in patients with obstructive hypertrophic cardiomyopathy (HCM) submitted to pacing.

DESIGN: Prospective, observational study.

SETTING: Single, non-referral centre.

PATIENTS AND INTERVENTION: Fifty patients (62 + or - 11 years) with HCM refractory to medical treatment, all in New York Heart Association (NYHA) class III or IV, and with a rest gradient >50 mm Hg underwent a dual-chamber pacemaker implantation. Patients were followed-up for up to 10 years (mean 5.0 + or - 2.9, range 0.6-10.1).

RESULTS: During the first year of follow-up, rest gradients decreased (baseline 86 + or - 29 mm Hg; 3 months 55 + or - 37; l year 41 + or - 26; p=0.0001). NYHA class improved, as well as exercise tolerance (baseline 281 + or - 112 m; 3 months 334 + or - 106 m; 1 year 348 + or - 78 m; p<0.0001). The physical and mental components of the quality of life instrument SF-36 also improved. Left ventricular wall thickness remained unchanged, while ejection fraction decreased (baseline 76 + or - 10%; 3 months 74 + or - 8%; 1 year 66 + or - 13%; p=0.002). During the long-term follow-up, an additional reduction in obstruction was found (final rest gradient 28 + or - 24 mm Hg, p<0.02). Those patients who did not improve to NYHA class I or II and continued to have obstruction were given other treatments (six, alcohol ablation; three, surgical myectomy).

CONCLUSIONS: Pacing in HCM results in a significant reduction in obstruction, improvement of symptoms and exercise capacity that is progressive and may be achieved after a long period of time. In this series, only 18% of cases needed a more aggressive treatment to relieve residual obstruction and obtain a satisfactory symptomatic status. In conclusion, these results emphasise the need for new controlled studies of pacing with a longer follow-up.