Exercise stress echocardiography has been used for the diagnosis of pulmonary hypertension, but with variable protocols and uncertain limits of normal. We therefore used echocardiography to investigate the pulmonary hemodynamic response to progressively increased workload in 25 healthy volunteers aged from 19 to 62 yrs (mean 36).
Mean Ppa (mPpa) was estimated from the maximum velocity of tricuspid regurgitation (TR) and calculated as 0.6 x sPpa + 2 mmHg. Cardiac output (Q) was calculated from the aortic velocity-time integral, and left atrial pressure(Pla) estimated from the ratio of mitral flow E and tissue Doppler annulus E’ waves. The measurements were performed at baseline, at each level of workload increased by 20 W/ 2 min, and after 5, 10, 15 and 20 min of recovery. Slopes and extrapolated pressure intercepts of multipoint mPpa vs Q were calculated after Poon's adjustment for individual variability.
The maximum workload was 170+/−51 W (mean +/− SD), with a heart rate of 159+/−21 bpm. Systolic Ppa increased from 19+/−5 to 46+/−11 mmHg, and decreased to 27+/−7 and 20+/−5 mmHg after respectively 5 and 20 min recovery. Cardiac output increased from 4.7+/−1.0 to 18.0+/−4.2 L/min, and decreased to 7.2+/−1.8 and 5.3+/−1.2 L/min after 5 and 20 min of recovery. Systolic Ppa exceeded 40 mmHg in 19 of the 25 subjects. The slope of mPpa-Q was 1.34+/−0.72 mmHg/L/min with an extrapolated pressure intercept of 7.8+/−3.7 mmHg, not different from Pla which was at 8.0+/−1.7 mmHg. A distensibility coefficient was calculated at 0.0181+/−0.020 mmHg-1. These values are similar to previously reported in invasive studies (Reeves, Am J Physiol 2005;288:L419). The multipoint mPpa-Q were best described by a linear approximation with no discernable pattern.
(1)Normal pulmonary vascular pressure flow relationships can be defined by an incremental resistance of 1.34 mmHg/L/min with an upper limit (mean + 2SD) of 2.78 mmHg/L/min.(2)Measurements during recovery are unreliable because of rapid return to baseline.
Exercise stress echocardiography of the pulmonary circulation is feasible and provides realistic pulmonary hemodynamic measurements.
Paola Argiento, No Financial Disclosure Information; No Product/Research Disclosure Information