A team of researchers led Dr. Guido Claessen at the University Hospitals Leuven in Belgium recently published in the journal Heart their findings concerning the evaluation of chronic thromboembolic pulmonary hypertension (CTEPH) during exercise and the effects of administering sildenafil. The study is entitled “Exercise pathophysiology and sildenafil effects in chronic thromboembolic pulmonary hypertension.”
CTEPH can be a life-threatening condition, caused by repeated or unresolved pulmonary embolism (clots in the pulmonary arteries). Normally, the pulmonary embolism either resolves by itself or is successfully treated with medication. In situations where the clot is not disintegrated with medication, or there is a frequent recurrence of clots, the lungs may suffer vascular alterations that can lead to an abnormally high blood pressure in the pulmonary arteries – pulmonary hypertension.
CTEPH symptoms are mainly manifested during exercise, with the individuals experiencing shortness of breath and fatigue. The hemodynamic evaluation of the individual is usually performed at rest.
Researchers hypothesized that instead of performing resting measurements, exercise imaging of the right ventricular function of the patients would provide more insight into the limitations during exercise, as well as on the effects of the administration of pulmonary vasodilators.
To test their hypothesis, the team conducted cardiopulmonary tests among 14 CTEPH patients and 7 healthy individuals (control group). Cardiac magnetic resonance imaging (MRI) was performed both at rest and during supine bicycle exercise, along with invasive measurement of mean pulmonary arterial pressure (mPAP) before and after sildenafil, a medication used to treat pulmonary arterial hypertension.
Researchers observed that during exercise, CTEPH patients experienced a greater increase in mPAP/cardiac output ratio. The stroke volume index (SVi), which is the volume of blood pumped by the heart with each beat divided by the surface area of the patient’s body, was increased during exercise but only in the controls and not in CTEPH patients. Similar results were also obtained for the right ventricular ejection fraction (RVEF). Sildenafil administration decreased the mPAP/ cardiac output ratio and increased SVi and RVEF in CTEPH patients during exercise, but not in the healthy controls.
The team concluded that assessing the right ventricular function during exercise is more informative and can better explain the differences in exercise capacity observed in CTEPH patients, than assessing the right ventricular function in a resting state.