Continuous Electrocardiographic Recording During Exercise: Its Use in Evaluating the Effect of Pentaerythritol Tetranitrate

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Abstract
Modifications of the ecg equipment used for the continuous recording of the ecg during exercise are described. The continuous recording of the ecg during exercise permits the early identification of ischemic and rhythmic changes, thereby greatly enhancing the safety of this procedure. The continuous recording of the ecg during exercise provides a quantitative method for evaluating the effectiveness of an active drug such as pentaerythritol tetranitrate at any point during exercise and overcomes the disadvantage of the "all-or-none" interpretation occurring in the postexercise period. Using the QX:QT ratio rather than degree of RS-T segment depression appears to offer a convenient and reliable means with which to evaluate myocardial ischemia recorded during continuous exercise. Twenty milligrams of pentaerythritol tetranitrate (Peritrate) provided protection against pain induced by exercise in 100% of the patients studied 90 min. following its administration. Similar protection occurred in 45% of the patients 4 hr. after they had taken the drug. The maximal duration of protection of a 20-mg dose of pentaerythritol tetranitrate in some patients is between 1 1/2 and 4 hr. Twenty milligrams of pentaerythritol tetranitrate (Peritrate) prevents the occurrence of ischemic ecg changes (abnormal QX:QT ratio) induced by exercise. The duration of this "protection" is also between 1 1/2 and 4 hr in some patients. Further work is necessary to establish the precise duration of the protective action at this dosage level.