Complete abolition of the reentrant supraventricular tachycardia zone using a new modality of cardiac pacing with simultaneous atrioventricular stimulation.

In an attempt to prevent recurrent reentrant supraventricular tachycardia, an experimentally designed new pacemaker has been developed. The pacemaker, when connected to both atrial and ventricular electrodes, is capable of sensing either an atrial or ventricular signal and, in turn, triggers simultaneous atrioventricular A-V) stimulation. Efficacy of this pacemake was tested in four patients with recurrent paroxysmal A-V nodal reentrant tachycardia during electrophysiologic studies. After connection of the electrodes to the new pacemaker, all atrial or ventricular premature stimuli elicited simultaneous A-V stimulation with resultant impulse collision in the A-V junction. Consequently, the reentrant tachycardia zone was completely abolished in all patients. This study has thus demonstrated the clinical feasibility of simultaneous A-V pacing to abolish the supraventricular tachycardia zone in man.

Routine exercise ECG three weeks after acute myocardial infarction.

In the third week after acute myocardial infarction, mean 18 days, exercise tests have been performed in 209 patients prior to discharge from the Coronary Care Unit. The exercise was done on a bicycle ergometer with electrically controlled braking, starting at the load 300 kpm/min (equal to 50 W), increasing with 300 kpm/min every 6th min, aiming at a maximal symptom-limited performance. ECG, in 3 extremity leads and 3 precordial leads, and heart rate (HR) were continuously recorded, and blood pressure (BP) was measured every minute. The most common cause for discontinuing exercise was fatigue (in 58%). Anginal pain or dyspnoea was the cause in 23.8%. Only in 9.1% was the exercise interrupted by the investigator because of rhythm disturbances or pronounced ST-T changes. Maximal work varied from 1 min exercise at 300 kpm/min to 6 min at 900 kpm/min (150 W); 18% of all patients were able to work for 6 min at 600 kpm/min (100 W). HR increased on an average from 80 beats/min at rest to 129 beats/min at maximal work load. Systolic blood pressure (SBP) increased on an average from 126 to 170 mmHg. The maximal values reached during exercise were HR 170/min, and SBP 270 mmHg. The product HR X SPB increased a little more than two-fold on an average. ST-T changes indicating myocardial ischaemia during exercise were observed in 70%. During exercise ventricular ectopic beats occurred in 42%. All rhythm disturbances provoked by exercise disappeared spontaneously shortly after work. Persistent ECG changes, reinfarction or other serious complications were not observed in connection with the exercise test. It is concluded that an exercise test under controlled circumstances is safe in patients of all ages in the third week after myocardial infarction. It is an objective measure of physical work capacity and described the reaction to physical activity. It gives a basis for advising return to normal life and is of great psychological importance to the patient.