Standard ECG, Stress Testing

A1640JACC April 1, 2014

Volume 63, Issue 12

vALidAtion of A diAgnostic ALgorithm for cArdioPuLmonAry exercise testing: usefuLness in cLinicAL cArdioLogy

Moderated Poster ContributionsHall CSunday, March 30, 2014, 10:15 a.m.-10:30 a.m.

Session Title: ECG and Stress Testing: Predictive ValueAbstract Category: 27. Standard ECG, Stress Testing: ECG, Stress Testing, Sports and ExercisePresentation Number: 1205M-366C

Authors: Syed Hasan Yusuf, Mirza Nubair Ahmad, Mary Ellis, Haroon Yousaf, Timothy E. Paterick, Khawaja Afzal Ammar, Aurora Cardiovasc Svcs, Aurora Sinai/St. Luke’s Med Ctrs, Univ Wisconsin Sch Med and Public Health, Milwaukee, WI, USA, Div of Pulmonary & Critical Care Medicine, Med College of Wisconsin & Clement J. Zablocki VA Med Ctr, Milwaukee, WI, USA

Background: Only cardiopulmonary exercise (CPX) testing provides information on the ability of the cardiovascular system to meet the body’s metabolic demands in terms of oxygen consumption (VO2) and carbon dioxide production (VCO2). However, CPX testing is underutilized by cardiologists due to complex diagnostic algorithms involving up to 30 variables as well as lack of validation studies. We tested whether a 6-variable algorithm would discriminate cardiac from noncardiac causes of dyspnea when compared with comprehensive CPX testing to promote its use by cardiologists.

methods: Consecutive patients (n=54) referred for dyspnea underwent CPX test consisting of pulmonary (VO2, VCO2, 22 additional variables and invasive measurement of lactate and blood gasses at peak and baseline) and cardiac (exercise ECG, heart rate and blood pressure response) components and medical record evaluation. Patients were categorized as normal or abnormal by an experienced pulmonologist. Abnormal patients were further categorized according to cause of dyspnea (cardiac, pulmonary, deconditioning, poor effort and miscellaneous). Subsequently, the 6-variable algorithm was applied by a cardiologist blinded to all of the information from CPX tests, and the patients were categorized similarly. The 6 variables used were peak O2 uptake, peak respiratory exchange ratio, O2 pulse, heart rate reserve, breathing reserve (1 - [peak ventilation (VE)/maximal voluntary ventilation]) and ventilatory efficiency (VE/VCO2).

results: The 6-variable algorithm performed well against comprehensive CPX test in discriminating cardiac from noncardiac causes of dyspnea, with 94% sensitivity, 92% specificity, 84% positive predictive value, 97% negative predictive value and 93% accuracy. Kappa statistic revealed almost perfect agreement (0.834; p<0.0001), which remained consistent for gender and referral source.

conclusions: This is the first study to validate a diagnostic algorithm for patients undergoing CPX testing as well as demonstrate that a simplified 6-variable algorithm applied by a cardiologist without prior CPX experience is quite accurate. This may promote the use of CPX testing by cardiologists.