Do echocardiographic parameters correlate with cardiopulmonary exercise testing performance?

In the UK, the most common specialist investigation before major non-cardiac surgery is transthoracic echocardiography, which has a low positive predictive value for identifying peri-operative cardiac events [1]. By comparison, functional cardiorespiratory fitness determined by cardiopulmonary exercise testing (CPET) does predict postoperative outcomes after many surgical interventions [2]. We aimed to assess the correlation between echocardiographic measurement of left ventricular function and CPET performance.

Methods

Using a retrospective analysis of all patients undergoing CPET over a 75-month period, we extracted those who had an echocardiogram within 90 days of CPET (pre- or postoperatively), where there was no history of myocardial infarction between tests. We compared commonly reported CPET variables with echocardiographic measurement of left ventricular function (ejection fraction).

Data were analysed using Spearman rank correlation and Pearson correlation coefficient tests and presented as scatter plots.

Results

There were 1304 patients who had undergone CPET between 2009 and 2016 (461 female, 843 male, age range 18–94 years). Of these, 146 patients had echocardiograms performed within 90 days of CPET testing (54 female and 92 male, age range 24–89 years). The majority of patients (49%) were listed for major colorectal surgery. There was no correlation between anaerobic threshold (AT) (r = 0.04, p = 0.61), peak VO2 (r = −0.10, p = 0.23), ventilatory equivalent for CO2 (VE/VCO2) (r = −0.07, p = 0.38) and exercise time with left ventricular ejection fraction (r = −0.07, p = 0.44) (Fig. 1).

image

Figure 1 A: AT vs. ejection fraction, B: Peak VO2 vs. ejection fraction, C: VE/VCO2 vs. ejection fraction and D: exercise time vs. ejection fraction.

Discussion

There appears to be no correlation between ejection fraction measured by echocardiography and commonly reported CPET variables. Routine pre-operative echocardiography does not therefore appear to predict functional capacity. CPET variables have been shown to predict outcomes in non-cardiac surgery and these data would suggest that ejection fraction measured by resting echocardiography should not be used as a surrogate for functional capacity in order to infer pre-operative fitness and postoperative survival.

References

1. Wijeysundera DN, Beattie WS, Karkouti K, Neuman MD, Austin PC, Laupacis A. Association of echocardiography before major elective non-cardiac surgery with postoperative survival and length of hospital stay: population based cohort study. British Medical Journal 2011; 342: d3695.

2. Smith TB, Stonell C, Purkayastha S, Paraskevas P. Cardiopulmonary exercise testing as a risk assessment method in non cardio-pulmonary surgery: a systematic review. Anaesthesia 2009; 64: 883–93.