Background: Combined stress echo and cardio-pulmonary tests visualize cardiac chambers in four well defined activity levels (rest, unloaded, anaerobic threshold [AT], and peak), allowing non invasive assessment of cardiac function, hemodynamics, and oxygen content difference (A-VO2 Diff) during all stages.
Objectives: Assess individual mechanisms of effort intolerance in patients with HFpEF, HFrEF or normal cardiac function using combined echo and cardio-pulmonary stress test.
Methods: Left ventricular volumes, stroke volume, S`, E/e`, VO2, and A-VO2 Diff were measured in all effort stages using ramp semi-recumbent cycle prolonged (at least 8 minutes) exercise in 45 consecutive subjects evaluated for effort intolerance [14 normal cardiac function, 16 HFpEF, and 15 HFrEF patients; age 56.5±16; 73% male].
Results: In HFpEF and HFrEF, the changes in VO2 were attenuated (between group p=0.003; group by time interaction p<0.0001), as well as peak heart rate (P=0.0001; P=0.0001), and stroke volume (P=0.006; P=0.0001). End diastolic volume to E/e` ratio (measure of compliance) was superior in HFrEF and normal patients at baseline but worsened in HFpEF and HFrEF at peak exercise (8.3±4 vs. 11.6±5 vs. 19.1±8; P=0.004; P=0.01). Functional mitral regurgitation worsened even during the unloaded stage mostly in patients with HFrEF but also in several patients with HFpEF. The combined protocol recognized several unique etiologies for effort intolerance, such as intolerance to beta blockers due to combined low compliance and chrontropic incompetence inducing prolonged diastasis at peak exercise, and poor physical fitness even in patients with markedly low rest low ejection fraction, allowing individualized therapy for each patient.
