RESULTS	Compared with the control the time to the start of myocardial ischaemia ( 1 mm ST segment depression ) during exercise significantly increased by 3.2 ( 0.6 ) min after nifedipine , by 4.6 ( 0.4 ) min after atenolol , and by 4.6 ( 0.5 ) min after the combination ; rate-pressure product ( beats/min .\