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CLINICAL RESEARCH: VALVULAR HEART DISEASE

Cardiopulmonary Exercise Testing Determination of Functional Capacity in Mitral Regurgitation

Physiologic and Outcome Implications

David Messika-Zeitoun, MD^_*, Bruce D. Johnson, PhD^_*, Vuyisile Nkomo, MD^_*, Jean-François Avierinos, MD^_*, Thomas G. Allison, PhD^_*, Christopher Scott, MS, A. Jamil Tajik, MD^_* and Maurice Enriquez-Sarano, MD^_*,_*

^_* Division of Cardiovascular Diseases and Internal Medicine
Section of Biostatistics, Mayo College of Medicine, Rochester, Minnesota

Manuscript received August 24, 2005; revised manuscript received January 27, 2006, accepted February 7, 2006.

^_* Reprint requests and correspondence: Dr. Maurice Enriquez-Sarano, Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905 (Email: sarano.maurice{at}mayo.edu).

OBJECTIVES: This study was designed to evaluate prevalence, determinants, and clinical outcome implications of reduced functional capacity (FC) in patients with organic mitral regurgitation (MR).

BACKGROUND: Evaluation of FC by exercise testing is rarely performed in MR because little is known about the clinical determinants and outcome implications of FC.

METHODS: Cardiopulmonary exercise testing (CPET) was prospectively performed in 134 asymptomatic patients with organic MR to assess FC (peak oxygen consumption [VO₂]) simultaneously to Doppler-echocardiographic quantitation of MR (effective regurgitant orifice [ERO]) and left ventricular (LV) systolic and diastolic function.

RESULTS: Peak VO₂ was 26 ± 6 ml/kg/min (96 ± 16% of age-predicted), but varied widely (57% to 145% of predicted) and was markedly reduced (84% of predicted) in 19% of patients. Although ERO of MR was univariately associated with reduced FC (26 vs. 9% with ERO 40 vs. <40 mm²), independent determinants of reduced FC were LV diastolic function (higher E/E' ratio, p = 0.006), atrial fibrillation (p = 0.01), and lower forward stroke volume (p = 0.03). Clinical events (death, heart failure, new atrial fibrillation) and clinical events or surgery were more frequent with than without reduced FC (3 years, 36 ± 14% vs. 13 ± 4%, p = 0.02; and 66 ± 11% vs. 29 ± 5%, p = 0.001, respectively), even adjusting (risk ratios 1.80 and 1.54 respectively, both p 0.03) for age and ERO.

CONCLUSIONS: In asymptomatic organic MR, FC quantitatively assessed by CPET is unexpectedly markedly reduced in one out of every four to five patients. Reduced FC is independently determined by consequences rather than severity of MR and predicts increased subsequent clinical events. Therefore, CPET frequently reveals functional limitations not detected clinically and is an important tool in managing patients with organic MR.

Abbreviations and Acronyms   CI = confidence interval   CPET = cardiopulmonary exercise testing   ERO = effective regurgitant orifice   FC = functional capacity   LA = left atrium   MR = mitral regurgitation   RER = respiratory exchange ratio   RR = risk ratio   RVol = regurgitant volume   VCO2 = carbon dioxide production   VE = minute ventilation   VO2 = oxygen consumption

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