Shub, Clarence

Background: Although a gradual increase in heart rate (HR) during dobutamine stress testing (DST) is desired, few data exists regarding whether this is similarly achieved in patients of widely varying body mass index (BMI). Whether difference in BMI contributes to variation in the hemodynamic and symptomatic response to dobutamine is also unknown. Methods: From prospectively acquired data of 2776 consecutive patients who underwent DST according to standard weight-based clinical protocol, we classified patients into 4 groups of BMI (kg/m 2 ): <25 (normal), 25 to 29.9 (overweight), 30 to 39.9 (obese), and ≥40 (severely obese) and compared the rate of increase of HR, mean blood pressure, and development of symptoms for the groups. Results: Age was 68 + 12 years, 52% were men, BMI was 29.8 + 6.6 kg/m 2 (range 14.5-81.4), 198 (7%) had BMI ≥40, and target HR was achieved in 2433 (88%). The rate of increase in HR was similar for each group of BMI after adjustment for age, gender, baseline HR, negative chronotropic use, and atropine administration. The percentage of patients in each group who achieved target HR was similar and the percentage of target HR achieved at each stage of dobutamine was essentially equivalent. Blood pressure responses and development of symptoms were similar in the 4 groups of BMI. Independent predictors of failure to achieve target HR included age, diabetes mellitus, treatment with negative chronotropic medications, and baseline HR; BMI was not a predictor (odds ratio [OR] 0.98, P = .086). Conclusion: The current weight-based protocol of dobutamine dosing for DST results in similar increases in HR and blood pressure for patients of widely varying BMI.

Background— The outcome of mitral valve prolapse (MVP) is controversial, with marked discrepancies in reported complication rates. Methods and Results— We conducted a community study of all Olmsted County, Minn, residents first diagnosed with asymptomatic MVP between 1989 and 1998 (N=833). Diagnosis, motivated by auscultatory findings (n=557) or incidental (n=276), was always confirmed by echocardiography with the use of current criteria. End points analyzed during 4581 person-years of follow-up were mortality (n=96, 19±2% at 10 years), cardiovascular morbidity (n=171), and MVP-related events (n=109, 20±2% at 10 years). The most frequent primary risk factors for cardiovascular mortality were mitral regurgitation from moderate to severe ( P =0.002, n=131) and, less frequently, ejection fraction <50% ( P =0.003, n=31). Secondary risk factors independently predictive of cardiovascular morbidity were slight mitral regurgitation, left atrium ≥40 mm, flail leaflet, atrial fibrillation, and age ≥50 years (all P <0.01). Patients with only 0 or 1 secondary risk factor (n=430) had excellent outcome, with 10-year mortality of 5±2% ( P =0.17 versus expected), cardiovascular morbidity of 0.5%/y, and MVP-related events of 0.2%/y. Patients with ≥2 secondary risk factors (n=250) had mortality similar to expected ( P =0.20) but high cardiovascular morbidity (6.2%/y, P <0.01) and notable MVP-related events (1.7%/y, P <0.01). Patients with primary risk factors (n=153) showed excess 10-year mortality (45±9%, P =0.01 versus expected), high morbidity (18.5%/y, P <0.01), and high MVP-related events (15%/y, P <0.01). Conclusions— Natural history of asymptomatic MVP in the community is widely heterogeneous and may be severe. Clinical and echocardiographic characteristics allow separation of the majority of patients with excellent prognosis from subsets of patients displaying, during follow-up, high morbidity or even excess mortality as direct a consequence of MVP.