Abstract
Background: Two-dimensional volumetric exercise stress echocardiography (ESE) provides an integrated view of left ventricular (LV) preload reserve through end-diastolic volume (EDV) and LV contractile reserve (LVCR) through end-systolic volume (ESV) changes. Purpose: To assess the dependence of cardiac reserve upon LVCR, EDV, and heart rate (HR) during ESE. Methods: We prospectively performed semi-supine bicycle or treadmill ESE in 1344 patients (age 59.8 ± 11.4 years; ejection fraction = 63 ± 8%) referred for known or suspected coronary artery disease. All patients had negative ESE by wall motion criteria. EDV and ESV were measured by biplane Simpson rule with 2-dimensional echocardiography. Cardiac index reserve was identified by peak-rest value. LVCR was the stress-rest ratio of force (systolic blood pressure by cuff sphygmomanometer/ESV, abnormal values ≤2.0). Preload reserve was defined by an increase in EDV. Cardiac index was calculated as stroke volume index * HR (by EKG). HR reserve (stress/rest ratio) <1.85 identified chronotropic incompetence. Results: Of the 1344 patients, 448 were in the lowest tertile of cardiac index reserve with stress. Of them, 303 (67.6%) achieved HR reserve <1.85; 252 (56.3%) had an abnormal LVCR and 341 (76.1%) a reduction of preload reserve, with 446 patients (99.6%) showing ≥1 abnormality. At binary logistic regression analysis, reduced preload reserve (odds ratio [OR]: 5.610; 95% confidence intervals [CI]: 4.025 to 7.821), chronotropic incompetence (OR: 3.923, 95% CI: 2.915 to 5.279), and abnormal LVCR (OR: 1.579; 95% CI: 1.105 to 2.259) were independently associated with lowest tertile of cardiac index reserve at peak stress. Conclusions: Heart rate assessment and volumetric echocardiography during ESE identify the heterogeneity of hemodynamic phenotypes of impaired chronotropic, preload or LVCR underlying a reduced cardiac reserve.
Highlights
The goal of the heart during exercise is to increase cardiac output (CO) to metabolizing tissues [1]
We identified four main subgroups: normal heart; abnormal heart; a group with two abnormalities and a group with 1 abnormality
Lower heart rate (HR) increase, end-diastolic volume (EDV) decrease at stress, and abnormal LV contractile reserve (LVCR) were associated with an increased likelihood of reduced cardiac reserve (Table 3)
Summary
The goal of the heart during exercise is to increase cardiac output (CO) to metabolizing tissues [1]. Cardiac reserve is defined as an appropriate increase in CO during stress and requires adequate contractile, preload and chronotropic reserves [1]. During treadmill or bicycle exercise, heart rate (HR) normally increases two- to three-fold, left ventricular contractile reserve (LVCR) three- to four-fold, and systolic blood pressure by ≥50%, while systemic vascular resistance decreases. Twodimensional volumetric exercise stress echocardiography (ESE) provides an integrated view of preload reserve through EDV and LVCR through end-systolic volume (ESV) changes. Two-dimensional volumetric exercise stress echocardiography (ESE) provides an integrated view of left ventricular (LV) preload reserve through end-diastolic volume (EDV) and LV contractile reserve (LVCR) through end-systolic volume (ESV) changes. Purpose: To assess the dependence of cardiac reserve upon LVCR, EDV, and heart rate (HR) during ESE. LVCR was the stress-rest ratio of force (systolic blood pressure by cuff sphygmomanometer/ESV, abnormal values ≤2.0). 303 (67.6%) achieved HR reserve
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