The impact of arterial load on left ventricular performance: an invasive haemodynamic study in severe mitral stenosis

Abstract

Key pointsr A hallmark of mitral stenosis (MS) is the markedly altered left ventricular (LV) loading. r As most of the methods used to determine LV performance in MS patients are influenced by loading conditions, previous studies have shown conflicting results.r The present study calculated LV elastance, which is a robust method to quantify LV function.We demonstrate that LV loading in MS patients is elevated but normalizes after valve repair and might be a result of reflex pathways.r Additionally, we show that the LV in MS is less compliant than normal due to a combination of right ventricular loading and the valvular disease itself. Immediately after valve dilatation the increase in blood inflow into the LV results in even greater LV stiffness.r Our findings enrich our understanding of heart function in MS patients and provide a simple reproducible way of assessing LV performance in MS.Abstract Left ventricular (LV) function in rheumatic mitral stenosis (MS) remains an issue of controversy, due to load dependency of previously employed assessment methods. We investigated LV performance in MS employing relatively load-independent indices robust to the altered loading state. We studied 106 subjects (32 ± 8 years, 72% female) with severe MS (0.8 ± 0.2 cm 2 ) and 40 age-matched controls. MS subjects underwent simultaneous bi-ventricular catheterization and transthoracic echocardiography (TTE) before and immediately after percutaneous transvenous mitral commisurotomy (PTMC). Sphygmomanometric brachial artery pressures and TTE recordings were simultaneously acquired in controls. Single-beat LV elastance (E es ) was employed for LV contractility measurements. Effective arterial elastance (E a ) and LV diastolic stiffness were measured. MS patients demonstrated significantly elevated afterload (E a : 3.0 ± 1.3 vs. 1.5 ± 0.3 mmHg ml −1 ; P < 0.001) and LV contractility (E es : 4.1 ± 1.6 vs. 2.4 ± 0.5 mmHg ml −1 ; P < 0.001) as compared to controls, with higher E a in subjects with smaller mitral valve area (ࣘ 0.8 cm 2 ) and pronounced subvalvular fusion. Stroke volume (49 ± 16 to 57 ± 17 ml; P < 0.001) and indexed LV end-diastolic volume (LVEDV index : 57 ± 16 to 64 ± 16 ml m −2 ; P < 0.001) increased following PTMC while E es and E a returned to more normal levels. Elevated LV stiffness was demonstrated at baseline and increased further following PTMC. Our findings provide evidence of elevated LV contractility, increased arterial load and increased diastolic stiffness in severe MS. Following PTMC, both LV contractility and afterload tend to normalize.A. Manouras and A. I. Nagy contributed equally to this study.

Left ventricular diastolic function in mitral stenosis

“…In this study, increased LV chamber stiffness normalized after balloon intervention 6 . Other mechanisms proposed to explain reduced LV compliance in MS include restriction of regional myocardial segments 13 and the influence of a dilated, overloaded right heart on left‐sided distensibility 19,38 . Negative diastolic pressures have been demonstrated in MS which characterizes ventricular early diastolic suction 34 .…”

“…In the 1950s, studies by Harvey 1 and Fleming 2 explored mechanistic theories related to the presentation of depressed LV function in MS. Surgical commissurotomy was widely considered as an effective therapy to relieve symptoms at that time, and the ability to distinguish patients with mechanical obstruction that may benefit from surgery from those with primary myocardial insufficiency held clinical and prognostic relevance. Several studies have subsequently reported reduced pump performance in this setting 3‐8 and have attributed this to variable mechanisms that include impaired LV filling secondary to mitral valvular obstruction, 9‐11 chronic myocardial inflammation, 12‐14 sub‐valvular scarring resulting in regional abnormalities, 3,15,16 elevated systemic load, 4,17‐19 and right–left interactions 20 (Table 1).…”

The effects of graded changes in oxygen and carbon dioxide tension on coronary blood velocity independent of myocardial energy demand

“…Recently, an index of left ventricular (LV) function has been developed using a noninvasive estimation of myocardial elastance that allows an investigator to assess the elastic potential energy of the heart (7). This index is well correlated with invasive measures of myocardial contractility and has been adopted for clinical assessments of LV function (38,40,52). Along with noninvasive LV pressure and volume estimations, it can be used to generate noninvasive pressure volume relationships, which might provide a less variable index of total mechanical energy than RPP.…”

Impact of left atrial compliance improvement on functional status after percutaneous mitral valvuloplasty

“…Reduced C v has been attributed to a functional restriction related to the thickened immobile valve apparatus tethered to the ventricular chamber rather than a permanent myocardial abnormality . Therefore, PMV sufficiently improves valve apparatus mobility to release this constraining effect on the ventricle, thereby revealing relatively normal underlying myocardial chamber properties …”

“…Reduced C v has been attributed to a functional restriction related to the thickened immobile valve apparatus tethered to the ventricular chamber rather than a permanent myocardial abnormality. 27,28 Therefore, PMV sufficiently improves valve apparatus mobility to release this constraining effect on the ventricle, thereby revealing relatively normal underlying myocardial chamber properties. 27 Previous studies addressing the impact of atrial compliance on pulmonary artery pressure have used net atrioventricular compliance (C n ), derived by Doppler echocardiography, 29 which is comparable to invasively measured C av .…”