Cardiac stunning during haemodialysis: the therapeutic effect of intra-dialytic exercise

Abstract

Background: Cardiovascular risk is elevated in end-stage renal disease. Left ventricular (LV) dysfunction is linked to repetitive transient ischaemia occurring during haemodialysis (HD). Cardiomyocyte ischaemia results in 'cardiac stunning', evidenced by regional wall motion abnormalities (RWMAs). Ischaemic RWMA have been documented during HD resulting in maladaptive cardiac remodelling and increased risk of heart failure. Intra-dialytic exercise is well tolerated and can improve quality of life and functional capacity. It may also attenuate HD-induced cardiac stunning.

Methods: This exploratory study aimed to assess the effect of intra-dialytic cycle ergometry on cardiac stunning. Twenty exercise-naïve participants on maintenance HD (mean ± SD, 59 ± 11 years) underwent resting echocardiography and maximal cardiopulmonary exercise testing. Subsequently, cardiac stunning was assessed with myocardial strain-derived RWMAs at four time points during (i) standard HD and (ii) HD with 30 min of sub-maximal intra-dialytic cycle ergometry at a workload equivalent to 90% oxygen uptake at the anaerobic threshold (VO₂AT). Central haemodynamics and cardiac troponin I were also assessed.

Results: Compared with HD alone, HD with intra-dialytic exercise significantly reduced RWMAs after 2.5 h of HD (total 110 ± 4, mean 7 ± 4 segments versus total 77 ± 3, mean 5 ± 3, respectively; P = 0.008). Global cardiac function, intra-dialytic haemodynamics and LV volumetric parameters were not significantly altered with exercise.

Conclusions: Intra-dialytic exercise reduced cardiac stunning. Thirty minutes of sub-maximal exercise at 90% VO₂AT was sufficient to elicit acute cardio-protection. These data potentially demonstrate a novel therapeutic effect of intra-dialytic exercise.

Keywords: end-stage renal disease; global longitudinal strain; regional wall motion abnormality.

FIGURE 1

Schematic for HD and HD + CLE tests. Black bars indicate data collection time points: (i) pre-HD; (ii) 1 h-HD (pre-exercise); (iii) 1.5 h-HD (post-exercise); and (iv) 2.5 h-HD (1 h post-exercise). Dashed box indicates cycle ergometry during HD + CLE. Echo, echocardiogram.

FIGURE 2

Typical echocardiogram assessment during HD. (A) Apical four-chamber view, (B) apical two-chamber view, (C) apical three-chamber view. Images A and B were used to calculate LV stroke volume, cardiac output, ejection fraction and end-diastolic and -systolic volumes with the Simpson’s biplane method. Images A–C were used for GLS and RWMA assessment, and subsequently, a bullseye plot was produced (D). Dark grey indicates higher longitudinal strain with light grey and white indicating progressively lower longitudinal strain (hypokinesia). A score of 0 (white) indicates myocardial segment akinesia.

FIGURE 3

Regional bullseye plot of the left ventricle for identification of longitudinal strain and RWMAs. Each segment represents local myocardial function. ANT, anterior; LAT, lateral; POST, posterior; INF, inferior; SEPT, septal; ANT-SEP, anterior septal.

FIGURE 4

Cardiac function and troponin I during HD and HD + CLE conditions. Filled diamond indicates HD + CLE condition; filled square indicates HD condition. (A) HR, (B) ejection fraction, (C) cardiac output, (D) stroke volume, (E) LV end-diastolic volume, (F) LV end-systolic volume, (G) mean RWMAs, (H) GLS and (I) cardiac troponin I. Grey boxes indicate 30-min exercise period for HD + CLE. *Significant difference between HD + CLE and HD conditions.

FIGURE 4

Cardiac function and troponin I during HD and HD + CLE conditions. Filled diamond indicates HD + CLE condition; filled square indicates HD condition. (A) HR, (B) ejection fraction, (C) cardiac output, (D) stroke volume, (E) LV end-diastolic volume, (F) LV end-systolic volume, (G) mean RWMAs, (H) GLS and (I) cardiac troponin I. Grey boxes indicate 30-min exercise period for HD + CLE. *Significant difference between HD + CLE and HD conditions.

FIGURE 5

Mean regional longitudinal strain of the LV demonstrated using bullseye plots during pre-HD (A and B), 1 h-HD (C and D), 1.5 h-HD (E and F) and 2.5 h-HD (G and H) for HD (left column) and HD + CLE (right column). Dark grey indicates higher longitudinal strain, light grey indicates lower longitudinal strain (hypokinesia). For a detailed explanation of each segment and its myocardial representation, see Figure 3.

FIGURE 6

Intra-dialytic haemodynamics as SBP and DBP (A) and MAP (B). Grey boxes indicate the 30-min exercise period for HD + CLE.