Clinical guidelines for pulmonary hypertension recommend evaluating treatment response through various methods; however, electrocardiography (ECG) is not included as one of the methods of choice. We aimed to identify ECG parameters that correlated with prognosis in patients with pulmonary arterial hypertension (PAH). A total of 112 consecutive patients with PAH were enrolled in this study. Among them, 83 with treatment escalation were studied for further analysis. Survival analyses were conducted using the Kaplan–Meier method with the log-rank test. Cox proportional hazards regression modeling was used to identify predictors of survival. Receiver operating characteristic analysis was used to determine cut-off values for selected variables. ECG parameters were changed from baseline to three months after treatment. Patients in whom the R wave amplitude in lead V1 decreased by ≥1 mm (0.1 mV) within three months demonstrated significantly better survival (P = 0.017). Our results suggest that evaluation of ECG parameters can contribute to assessments of survival in patients with PAH.