Aims To analyse whether heart rate may affect the efficacy of adenosine , verap amil and carotid sinus massage in terminating symptomatic episodes of paroxysmal supraventricular tachycardia (PSVT) in adults. Methods and results The study po pulation was selected among 175 adult patients, affected by symptomatic PSVT. On e hundred and six of them were considered eligible for the study. Each subject r eceived one of the following treatments: verapamil, 5 mg intravenously (IV) in 5 -10 min, followed by 1-5 μg/kg/min; adenosine, 6 mg IV, followed by 12 mg IV after 2-3 min; carotid sinus massage. Adenosine and verapamil were similarly ef fective in terminating PSVT (74.4%vs 81.8%, P=0.45). The efficacy of carotid s inus massage was significantly lower in comparison with the other two groups (32 .4%, P=0.00032 vs adenosine and P=0.000044 vs verapamil group). At logistic reg ression, PSVT rate showed a positive association with the percentage of sinus rh ythm restoration in the group who received adenosine (P=0.0004). The probability of success in resolving the tachycardia following treatment with adenosine was >75%for heart rates over 166 beats per minute (bpm), but rapidly decreased at l ower frequencies, reducing to 25%at 138 bpm. In the verapamil group, PSVT rate was negatively related to the percentage of sinus rhythm restoration (P=0.018). The probability of success in terminating PSVT following administration of verap amil was >75%for heart rates lower than 186 bpm, but tended to decrease at fast er rates, reducing to 25%at 241 bpm. No significant effects of heart rate were observed in the carotid sinus massage group (P=0.17). The probability curves obt ained in the adenosine and verapamil group crossed at a point corresponding to 1 73 bpm, which may represent a cut-off value to predict which treatment could en sure higher rate of success. Conclusions Heart rate predicts restoration of sinu s rhythm in adult subjects with symptomatic episodes of PSVT treated with adenos ine and verapamil. Adenosine is highly effective in PSVT characterised by fast r ates, whereas the efficacy of verapamil is increased in patients with low-frequ ency PSVT. Aims To analyze whether the efficacy of adenosine, verap amil and carotid sinus massage in terminating symptomatic episodes of paroxysmal supraventricular tachycardia (PSVT) in adults. Methods and results The study po pulation was selected among 175 adult patients, affected by symptomatic PSVT. On e hundred and six of them were considered eligible for the study. Each subject r eceived one of the following treatments: verapamil, 5 mg intravenously (IV) in 5-10 min followed by 1-5 μg / kg / min ; adenosine, 6 mg IV followed by 12 mg IV after 2-3 min; carotid sinus massage. Adenosine and verapamil were similarly fective in terminating PSVT (74.4% vs 81.8%, P = 0.45). The efficacy of carotid s inus massage was significantly lower in comparison with the other two groups (32.4%, P = 0.00032 vs adenosine and P = 0.000044 vs verapamil group). At logistic reg ression, PSVT rate showed a positive association with the percentage of sinus rh ythm restoration in the group who rec The probability of success in resolving the tachycardia following treatment with adenosine was> 75% for heart rates over 166 beats per minute (bpm), but rapidly decreased at lower frequencies, reducing to 25% at 138 bpm. In the verapamil group, PSVT rate was negatively related to the percentage of sinus rhythm restoration (P = 0.018). The probability of success in terminating PSVT following administration of verap amil was> 75% for heart rates lower than 186 bpm, but tended to decrease at faster rates, reducing to 25% at 241 bpm. No significant effects of heart rate were observed in the carotid sinus massage group (P = 0.17). The probability curves obt ained in the adenosine and verapamil group crossed at a point corresponding to 1 73 bpm, which may represent a cut-off value to predict which treatment could en sure higher rate of success. Conclusions Heart rate predicts restoration of sinu s rhythm in adult subjects with symptomatic episodes of PSVT treated with a denos ine and verapamil. Adenosine is highly effective in PSVT characterized by fast r ates, and the efficacy of verapamil is increased in patients with low-frequ ency PSVT.