Contractile reserve and cardiopulmonary exercise parameters in patients with dilated cardiomyopathy, the two dimensions of exercise testing

Moneghetti KJ, Kobayashi Y, Christle JW, Ariyama M, Vrtovec
B, Kouznetsova T, Wilson A, Ashley E, Wheeler MT,
Myers J, Haddad F

Echocardiography. 2017 Aug;34(8):1179-1186. doi: 10.1111/echo.13623. Epub 2017
Jul 6

BACKGROUND: Left ventricular (LV) contractile reserve assessed using imaging and
cardiopulmonary exercise testing (CPX) has been shown to predict outcome in
patients with dilated cardiomyopathy (DCM). Few clinical studies have, however,
analyzed the relationship between them.
METHODS: A cohort of 75 ambulatory patients with DCM underwent stress treadmill
echocardiography with CPX. LV contractile reserve was calculated as absolute
change (ΔLVEF=LVEFpeak -LVEFrest ) and percent change (%LVEF=[(LVEFpeak -LVEFrest
)/LVEFpeak) ]×100) in LVEF, circumferential and longitudinal strain (LS).
Exercise capacity was measured as peak oxygen uptake (peak VO2 ) and ventilatory
efficiency as the slope of minute ventilation to CO2 production (VE/VCO2 slope).
Values of contractile reserve were compared to matched controls. We also explored
which metric of ventricular response (absolute or percent change) was less
dependent on baseline LV function.
RESULTS: Patients with DCM had a mean age, rest and peak LVEF of 44±10 years,
42±10% and 50±12%, respectively. Among parameters of contractile reserve, peak
cardiac output was the strongest parameter associated with peak VO2 (r=.63,
P<.001). Along with age, sex, and BMI, it explained more than 70% of the variance
in peak VO2 . In contrast, LVEF and LS were only weakly related to peak VO2 .
With regard to ventilatory efficiency, the strongest parameter that emerged was
right atrial volume index (r=.36, P<.001). Percent change in LVEF was more
independent of baseline function than absolute change.
CONCLUSION: Echocardiographic contractile reserve and CPX provide complementary
information. Percent change in contractile reserve was most independent of
baseline function, therefore may be preferred when analyzing the ventricular
response to exercise.