Angina pectoris with normal coronary arteries

Exercise-based cardiac rehabilitation for adults after heart valve surgery

BACKGROUND

The impact of exercise-based cardiac rehabilitation (CR) following heart valve surgery is uncertain. We conducted an update of this systematic review and a meta-analysis to assess randomised controlled trial evidence for the use of exercise-based CR following heart valve surgery.

OBJECTIVES

To assess the benefits and harms of exercise-based CR compared with no exercise training in adults following heart valve surgery or repair, including both percutaneous and surgical procedures. We considered CR programmes consisting of exercise training with or without another intervention (such as an intervention with a psycho-educational component).

SEARCH METHODS

We searched the Cochrane Central Register of Clinical Trials (CENTRAL), in the Cochrane Library; MEDLINE (Ovid); Embase (Ovid); the Cumulative Index to Nursing and Allied Health Literature (CINAHL; EBSCO); PsycINFO (Ovid); Latin American Caribbean Health Sciences Literature (LILACS; Bireme); and Conference Proceedings Citation Index-Science (CPCI-S) on the Web of Science (Clarivate Analytics) on 10 January 2020. We searched for ongoing trials from ClinicalTrials.gov, Clinical-trials.com, and the World Health Organization International Clinical Trials Registry Platform on 15 May 2020.

SELECTION CRITERIA

We included randomised controlled trials that compared exercise-based CR interventions with no exercise training. Trial participants comprised adults aged 18 years or older who had undergone heart valve surgery for heart valve disease (from any cause) and had received heart valve replacement or heart valve repair. Both percutaneous and surgical procedures were included.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data. We assessed the risk of systematic errors ('bias') by evaluating risk domains using the 'Risk of bias' (RoB2) tool. We assessed clinical and statistical heterogeneity. We performed meta-analyses using both fixed-effect and random-effects models. We used the GRADE approach to assess the quality of evidence for primary outcomes (all-cause mortality, all-cause hospitalisation, and health-related quality of life).

MAIN RESULTS

We included six trials with a total of 364 participants who have had open or percutaneous heart valve surgery. For this updated review, we identified four additional trials (216 participants). One trial had an overall low risk of bias, and we classified the remaining five trials as having some concerns. Follow-up ranged across included trials from 3 to 24 months. Based on data at longest follow-up, a total of nine participants died: 4 CR versus 5 control (relative risk (RR) 0.83, 95% confidence interval (CI) 0.26 to 2.68; 2 trials, 131 participants; GRADE quality of evidence very low). No trials reported on cardiovascular mortality. One trial reported one cardiac-related hospitalisation in the CR group and none in the control group (RR 2.72, 95% CI 0.11 to 65.56; 1 trial, 122 participants; GRADE quality of evidence very low). We are uncertain about health-related quality of life at completion of the intervention in CR compared to control (Short Form (SF)-12/36 mental component: mean difference (MD) 1.28, 95% CI -1.60 to 4.16; 2 trials, 150 participants; GRADE quality of evidence very low; and SF-12/36 physical component: MD 2.99, 95% CI -5.24 to 11.21; 2 trials, 150 participants; GRADE quality of evidence very low), or at longest follow-up (SF-12/36 mental component: MD -1.45, 95% CI -4.70 to 1.80; 2 trials, 139 participants; GRADE quality of evidence very low; and SF-12/36 physical component: MD -0.87, 95% CI -3.57 to 1.83; 2 trials, 139 participants; GRADE quality of evidence very low).  AUTHORS' CONCLUSIONS: Due to lack of evidence and the very low quality of available evidence, this updated review is uncertain about the impact of exercise-CR in this population in terms of mortality, hospitalisation, and health-related quality of life. High-quality (low risk of bias) evidence on the impact of CR is needed to inform clinical guidelines and routine practice.

Syndrome X and hyperventilation

The cardiorespiratory responses to exercise and forced hyperventilation were measured in 17 unselected patients with syndrome X (angina, positive exercise test, normal coronary arteriogram, no other cardiovascular disease) and compared with those in 15 healthy subjects. Forced hyperventilation produced hypocapnia and metabolic alkalosis but no chest pain or electrocardiographic change. Patients with syndrome X showed reduced maximum oxygen consumption with an increased respiratory exchange ratio at peak exercise, confirming that exercise was limited by skeletal muscle perfusion--and thus that the increase in cardiac output with exercise is limited in syndrome X as in heart failure. Arterial carbon dioxide tension (PCO2) homoeostasis during exercise was normal but the ventilatory cost of carbon dioxide excretion was increased in syndrome X (as in heart failure). End tidal PCO2 measurements correlated only poorly with arterial PCO2 in individual patients with syndrome X, providing a possible explanation for previous reports, based on end tidal PCO2 of inappropriate hyperventilation. Patients with syndrome X did not show inappropriate hyperventilation but they did show hyperventilation that was appropriate to maintain normal arterial PCO2 in the face of reduced cardiac reserve.

Syndrome X

The problem of anginalike chest pain with normal coronary arteriographic findings is briefly reviewed. This common clinical presentation (ca. 20% of patients investigated by coronary arteriography) is usually due to noncardiac causes (e.g., thoracic root or esophageal pain) but may represent myocardial ischemia attributable to reduced coronary dilator capacity downstream from the epicardial vessels and of unknown pathogenesis--Syndrome X (? less than 0.1% of such patients).