Comparison of mortality from acute myocardial infarction between 1979 and 1992 in a geographically defined stable population.

This study documents mortality from acute myocardial infarction (AMI), in hospital and at 1 year, for each of 3 selected 1-year periods in a stable community over a 13-year period beginning in 1979 and continuing into the thrombolytic era, to detect any changes occurring in conjunction with the introduction of new therapies. Every patient with AMI occurring in a geographically defined stable community (Hamilton, Ontario, Canada) in 3 1-year periods (1979 to 1980 [n = 816], 1986 to 1987 [n = 816], and 1991 to 1992 [n = 831]) was identified and clinically characterized by standardized criteria. Subsequent in-hospital and 1-year survival were ascertained prospectively. The 3 cohorts were similar in prognostic factors. Mean age was progressively greater over the study period from 63 years in 1979 to 1980, to 67 years in 1991 to 1992 (p = 0.02). There was no change in in-hospital mortality rates from 1979 to 1980 (17%) and 1986 to 1987 (16%). However, from 1986 to 1987 and 1991 to 1992, in-hospital mortality decreased from 16% to 9% (p < 0.001) and 1-year mortality decreased from 26% to 19% (p < 0.001). For patients who survived the hospital phase of AMI, 1-year mortality did not change and was between 11% and 12% in each of the 3 study periods. From 1986 to 1987 and 1991 to 1992, there was an increase in the use of thrombolytic therapy from 5% to 44% of patients. The acute use of aspirin increased from 30% to 88% and the acute use of beta blockers increased from 19% to 48% of patients. The observed increase in use of these agents could account for half of the actual mortality reduction observed. This prospective population-based survey demonstrates improved in-hospital survival after AMI associated with increased use of established effective therapies between 1987 and 1992. The 1-year mortality of hospital survivors of AMI was unchanged throughout the period of study, remaining at 11% to 12%.

Atrioventricular node reentry with 'smooth' AV node function curves: a different arrhythmia substrate?

BACKGROUND: Some patients with otherwise typical AV node reentry do not manifest discontinuous AV node function curves. We examined the effects of an ablation in the slow-pathway region in patients with smooth AV node function curves. METHODS AND RESULTS: Fifteen patients with AV node reentrant tachycardia (AVNRT) and discontinuous AV node function curves were compared with 15 patients with AVNRT and smooth AV node function curves. In the group with discontinuous curve, the "net" anterograde effective refractory period (AERP) of the AV node increased (270 +/- 28 versus 304 +/- 37 ms, P = .03) and AERP of the remaining fast pathway decreased (367 +/- 100 versus 304 +/- 37 ms, P = .026) after the ablation. In the group with a smooth curve, the AERP of the AV node increased (266 +/- 42 versus 299 +/- 76 ms, P = .07) and the anterograde Wenckebach cycle length increased (336 +/- 66 versus 379 +/- 86 ms, P = .008) after the ablation. Retrograde conduction over the AV node was similar in both groups and was unchanged after ablation. The longest attainable AH interval (AHmax) measured during atrial extrastimulus testing was more prolonged in patients with a discontinuous curve than in patients with a smooth curve (326 +/- 48 versus 250 +/- 70 ms, P = .002). The AHmax shortened in both groups after ablation (326 +/- 48 versus 173 +/- 34 ms, P < .0001, and 250 +/- 70 versus 179 +/ 34 ms, P < .0003, respectively) and were similar. Successful ablation in the slow-pathway zone in patients with a smooth AV node function curve resulted in the loss of the "tail" of the curve representing the slow pathway. CONCLUSIONS: These data suggest that the smooth AV node function curve consists of two distinct components representing both fast and slow AV node pathways even when the typical discontinuity is absent.