A 55-year-old male, who was diagnosed with emphysema 5 years earlier, had complaints of progressive dyspnea (New York Heart Association Class III) and cough during his regular visits to an outpatient clinic. In addition to the inhalant anticholinergics, he had taken a long acting beta-agonist and theophylline for his depressed ventilatory function (GOLD stage III). Despite a gradual exacerbation of dyspnea and an increase in the amount of sputum, there were no signs of other illnesses, including fever, myalgia or sore throat. His blood pressure was 135/80 mmHg, the pulse was 80 beats/min, the respiratory rate was 20 breaths/min and his temperature was 36.5℃. Electrocardiography showed right ventricular hypertrophy, and the chest X-rays showed no signs of pneumonia. The forced expiratory volume in 1 second (FEV₁) was 30% of the predicted value, and this had progressively worsened over the preceding year. Pulmonary arterial hypertension was noted on Doppler echocardiography with trivial tricuspidal regurgitation and a peak velocity (TR Vmax) of 3.6 m/s. The myocardial performance index (MPI) of the right ventricle (RV) was 0.56, which was not changed after 2 weeks of treatment. In addition to the baseline therapy, we administered tadalafil 10 mg orally every other day with the patient's informed consent. He well tolerated a 2 weeks course of this therapy, and he only complained of mild myalgia. Therefore, the tadalafil was increased up to 20 mg/every other day. After 4 weeks of tadalafil treatment, the TR Vmax was decreased to 3.2 m/sec and the MPI of the RV was improved to 0.42 (Table 1). His exercise capacity, as measured by the respiratory oxygen uptake, also improved from 10.9 mL/kg/min to 13.8 mL/kg/min.

A 62-year-old male presented with edema in his legs. He had been suffering from cor pulmonale associated with emphysema for 2 years. The latest data collected from the patient's visit to the clinic showed his ventilatory function being in GOLD stage IV. He was tachypneic (26 breaths/min) and had 3 + pitting edema of the legs. The patient's blood pressure was 120/75 mm Hg and his pulse was 105 beats/min. There were no notable exacerbating factors such as pneumonia, arrhythmia, pulmonary arterial embolism, etc. His arterial blood gas values were a PO₂ of 53 mmHg and a PCO₂ of 68 mmHg. Echocardiography showed dilated right chambers with severe tricuspidal regurgitation. The estimated TR Vmax was 4.1 m/sec and the MPI of the RV was 0.89. Although the patient's edema substantially improved after therapy with digitalis, diuretics, vasodilator and bronchodilator, the degree of pulmonary arterial hypertension did not change. Therefore, tadalafil therapy was attempted with the patient's written informed consent. We prescribed 10 mg of tadalafil orally every other day for 2 weeks and then we doubled the dosage. During 4 weeks of therapy, he complained of headache and mild orthostatic dizziness. Physical examination showed a blood pressure of 110/70 mmHg and the rest of the examination was unremarkable. Subjective improvement in his functional status was also noted (New York Heart Association Class II). The arterial PO₂ was 65 mmHg without inspired oxygen. His TR Vmax was also decreased to 3.7 m/sec and the MPI of the RV was improved to 0.6 (Table 1).