Clinical value of tests of sino-atrial function.
Sinus node recovery times and the premature atrial stimulus test were studied in 36 patients, seven with gross sinus node disease, 25 with possible sinus node disease and four with no clinical evidence of sinus node disease. The corrected sinus node recovery time proved of most value in predicting which patients needed and would benefit from permanent pacemaker implantation, though there was one false negative diagnosis and two patients with abnormal corrected sinus node recovery times were asymptomatic. The premature atrial stimulus test usually proved to be of no practical value once severe sinus node disease was present and, in the group of patients with suspected sino-atrial disease, only 13 of 25 graphs could be analysed due to gross "scatter" in the others. When patients with symptoms have unequivocal evidence of sino-atrial dysfunction, invasive study seems unnecessary. With lesser degrees of sino-atrial disease, premature atrial stimulation may provide confirmatory evidence; but when sinus arrhythmia, atrial escape beats, or more marked dysfunction are present, one is likely to encounter useless "scatter" graphs. In the absence of regular sinus rhythm on the ECG, overdrive sinus node suppression in the only invasive study worth attempting.