1000 Ventricular-vascular coupling is independently associated with exercise capacity in patients with ischemic cardiomyopathy: a cardiac multi-modality imaging study

Introduction

Left ventricular (LV) systolic dysfunction due to ischemic cardiomyopathy (I-CMP) leads to reduced exercise capacity. Ventricular-vascular coupling (VVC), a ratio of effective arterial to LV elastance, represents forward flow efficiency of LV, independent of mitral regurgitation.

Purpose

In I-CMP patients, we sought to a) assess relationship between resting VVC and maximum oxygen consumption corrected for peak heart rate (MVO₂/pHR), an accurate measure of exercise capacity in patients on β-blockers, and b) compare value of VVC versus other determinants of exercise capacity.

Methods

43 patients with I-CMP (age 59 ± 9 years, 88% on β-blocker) underwent cardiopulmonary exercise testing, echocardiography and cardiac magnetic resonance (CMR, 1.5 T Siemens Scanners, Erlangen Germany) for cardiac transplant evaluation. MVO₂/pHR and diastolic filling variables (echocardiography) were measured in a standard fashion. CMR LV indices [end-systolic (ESV), end-diastolic (EDV), stroke volume (SV), all in ml, and LVEF] were measured using the standard contiguous short-axis slices from apex to base, using the balanced steady state free precession cine sequence (TE = 1.6 msec, TR = 3.3 msec, flip angle = 70° and slice thickness 8–10 mm, field of view varied from 228–330 in the x-direction and 260–330 in the y-direction and matrix size varied from 140–180 in the x-direction and 256 in the y-direction, giving a spatial resolution of 1.5–2.1 mm (x-direction) by 1.1–1.4 mm (y-direction). For patients able to suspend respiration, breath hold duration was 10–15 sec, depending on the heart rate; otherwise, images were acquired using 3 signal averages. Subsequently, off-line analysis was performed using Argus analytical software (Siemens Medical Solutions, Erlangen, Germany) to assess LV volumes and LVEF, in a standard fashion. VVC was calculated as: [Effective arterial elastance (end systolic pressure ÷ stroke volume index)/LV end-systolic elastance (end systolic pressure ÷ LV systolic volume index)].

Results

Mean LVEF, ESV, EDV, and SV were 24 ± 8%, 228 ± 107 ml, 297 ± 111 ml, and 66 ± 20 ml respectively. Mean MVO₂/pHR was 13 ± 3 ml/beat. Predictors of MVO₂ are shown in Table 1. On stepwise regression, only VVC significantly predicted MVO₂/pHR.

Table 1 Univariate and multivariate predictors pf MVO₂/peak HR.

Conclusion

In I-CMP patients with LV dysfunction, VVC predicts MVO₂/pHR that can potentially be used as a potential therapeutic target.