Researchers in the Department of Cardiovascular Medicine at University Hospitals Leuven in Belgium found that measurement of the heart right ventricle (RV) function during exercise more accurately demonstrates the impaired exercise capacity of chronic thromboembolic pulmonary hypertension (CTEPH) patients compared to values obtained while patients are at rest. The study entitled “Exercise pathophysiology and sildenafil effects in chronic thromboembolic pulmonary hypertension” was published in the journal Heart on February 25, 2015.
CTEPH consists of high blood pressure in the pulmonary arteries for at least six months, often because of a pulmonary embolism, i.e. blockage of a pulmonary artery by a blood clot. Only about 5,000 people in the United States are diagnosed with CTEPH each year. In the early stages of the disease, the symptoms can be non-distinct, such as shortness of breath with exercise and fatigue — easily misdiagnosed as chronic obstructive pulmonary disorder (COPD). Later on, patients may feel faint and can show signs of right heart failure, such as fluid retention (edema) and blue-tinged fingers and toes (cyanosis).
The researchers wanted to test whether exercise rather than resting measurements of RV function would better explain exercise intolerance in CTEPH patients. To accomplish this, they evaluated patients’ and healthy participants’ biventricular volumes with simultaneous invasive haemodynamic measurements during exercise. They also wanted to understand the effects of sildenafil, a vasodilator, in improving exercise capacity in patients with CTEPH. Vasodilators determine peak exercise oxygen consumption and ventilatory equivalent for carbon dioxide at the anaerobic threshold of intense exercise.
Cardiac magnetic resonance (CMR) imaging studies were also performed at rest and during supine bicycle exercise with simultaneous invasive measurement of mean pulmonary arterial pressure (mPAP) before and after individuals were given sildenafil. The research team developed a CMR technique that allows real-time image acquisition during maximal exercise intensity and the study of several parameters of ventricular function. They found that these values changed differently between controls and patients during exercise and that sildenafil improved exercise performance and measured parameters in patients. Patients with CTEPH also had a greater increase in the ratio of mPAP relative to cardiac output compared to control individuals.
Considering the impact on clinical practice, “Exercise measures of RV function should be incorporated when evaluating patients with symptoms on exertion. Exercise cardiac MRI may be used as a non-invasive modality to evaluate the effect of novel pulmonary hypertension therapies on exercise haemodynamics and RV function,” explained the authors.