乌鸦传媒

Fewer people appear to be having heart attacks in recent years, and the number of patients who do seem to be surviving them -- at least in the short term, researchers have found.

The incidence of myocardial infarction (MI) seen among a cohort of more than 46,000 patients in Northern California decreased significantly since 2000, with a marked reduction in the incidence of ST-segment elevation MI (STEMI) after 1999 (P<0.001), according to Alan S. Go, MD, of Kaiser Permanente Northern California, and colleagues.

In addition, 30-day mortality rates for that patient population were considerably lower by 2008, falling from 10.5% in 1999 to 7.8% in 2008 (P<0.001 for linear trend), driven by a similar decline in deaths for non-STEMI, Go reported in the June 9 issue of the New England Journal of Medicine.

"The most striking finding was that the rate of the most serious heart attacks, the ST-elevation heart attacks, has decreased by 62% over the past decade within Kaiser Permanente," Go told 乌鸦传媒.

Numerous studies have found that prevention strategies to reduce myocardial infarction are effective, such as smoking bans, and these strategies have been implemented widely. Still, few studies have characterized recent trends for heart attacks in large patient populations, the researchers said.

So they assessed data from Kaiser Permanente Northern California on 46,086 MI hospitalizations between 1999 and 2008 for patients ages 30 and up.

The researchers found that MI incidence in this cohort increased from 274 cases per 100,000 person-years in 1999 to 287 cases per 100,000 person-years in 2000, but then decreased each year afterwards, falling to 208 cases per 100,000 person-years in 2008.

That represents a 24% relative decline over the study period, the researchers said.

The adjusted incidence of STEMI fell, too -- by 62% -- from 133 cases per 100,000 person-years in 1999 to 50 cases per 100,000 person-years in 2008 (P<0.001).

Incidence of non-STEMI increased, but that was likely due to increased screening for the biomarker troponin I, the researchers said. The proportion of patients who had troponin I testing increased from 53% in 1999 to 84% in 2004, with stable rates between 2004 and 2008. Incidence of non-STEMI appeared to level off again during this time.

Deaths from heart attacks among Kaiser Permanente patients also fell over the course of the study, declining from 10.5% in 1999 to 7.8% in 2008 (P<0.001). That translated to a 24% reduced risk of death in 2008 compared with 1999 (95% CI 0.65 to 0.89).

The researchers said the drop in mortality was "driven by the case fatality rate for non-STEMI," which fell from 10% to 7.6% over the course of the study (P<0.001). There was no change in the mortality rate among STEMI patients.

"It is not clear why the ST-segment elevation heart attacks in later years did not see lower mortality rates compared to earlier years," Go commented. "The ones in later years may just be more severe than earlier ones."

Finally, more Kaiser Permanente patients had revascularization within 30 days of suffering an MI in 2008 compared with 1999 (40.7% versus 47.2%, P<0.001).

The researchers attributed the decreased MI incidence and death partly to "substantial improvements in primary prevention efforts."

For example, the use of ACE inhibitors and ARBs, beta-blockers, and statins all increased significantly among Kaiser Permanente patients over the course of the study. Also, more patients in this cohort met target blood pressure levels during that time -- from 40% in 1999 to 80% in 2008.

The study was limited to patients of Kaiser Permanente Northern California, so the results may not be generalizable to other healthcare settings. Also, the true effect of changes in diagnostic sensitivity for troponin I testing can't be comprehensively quantified, and the expected bias would be an overestimation of MI incidence, they researchers said.

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