of 239 people with frequent pvcs (>1000 beats/day) and without structural heart disease (i.e. in the presence of normal heart function) there were no serious cardiac events through 5.6 years on average, but there was correlation between pvc prevalence and decrease of ejection fraction and increase of left ventricular diastolic dimension. in this study absence of heart of disease was established by echocardiography, cardiac magnetic resonance imaging in 63 persons and holter monitoring. another study has suggested that in the absence of structural heart disease even frequent (> 60/h or 1/min) and complex pvcs are associated with a benign prognosis. it was study of 70 people followed by 6.5 years on average. healthy status was verified by extensive noninvasive cardiologic examination, although cardiac catheterization of a subgroup disclosed serious coronary artery disease in 19%. overall survival was better than expected. on the other hand, the framingham heart study reported that frequent pvcs in healthy people were associated with a twofold increase in the risk of all-cause mortality, myocardial infarction and cardiac death. in men with coronary heart disease and in women with or without coronary heart disease, complex or frequent arrhythmias were not associated with an increased risk. the at-risk people might have subclinical coronary disease. these framingham results have been criticized for the lack of rigorous measures to exclude the potential confounder of underlying heart disease. in the aric study of 14,783 people followed for 15 to 17 years those with detected pvc during 2 minute ecg, and without hypertension or diabetes on the beginning, had risk of stroke increased by 109%. hypertension or diabetes, both risk factors for stroke, did not change significantly risk of stroke for people with pvcs. it is possible that pvcs identified those at risk of stroke with blood pressure and impaired glucose tolerance on a continuum of risk below conventional diagnostic thresholds for hypertension and diabetes. those in aric study with any pvc had risk of heart failure increased by 63% and were > twice as likely to die from coronary heart disease (chd). risk was also higher for people with or without baseline chd. in the niigata study of 63,386 people with a 10-year follow-up period, subjects with pvc during a 10-second recording had triple the risk of atrial fibrillation of those without pvcs, independently of these risk factors: age; male sex; high simple body mass index (a possible signifier of obesity); hypertension (systolic and diastolic blood pressure within certain abnormal limits); and diabetes. reducing very frequent pvc (>20%) by antiarrhythmic drugs or by catheter ablation significantly improves heart performance. recent studies have shown that those subjects with extremely frequent pvcs (several thousand a day) can develop dilated cardiomyopathy. in these cases, if the pvcs are reduced or removed (for example, via ablation therapy) the cardiomyopathy regresses. epidemiology single pvcs are common in healthy persons. when 24-hour ambulatory monitoring is used, up to 80 percent of apparently healthy people have occasional pvcs. rates vary by age with extremely rare for those under the age of 11 and extremely common in those older than 75 years. these differences may be due to rates of high blood pressure and atherosclerosis, which are more easy to find in older persons. in 101 people free of heart disease during 24 hours holter monitoring, 39 had at least 1 pvc, and 4 at least 100. heart disease was excluded after physical examination, chest x-ray, ecg, echocardiography, maximal exercise stress test, right- and left-heart catheterization and coronary angiography. in 122,043 united states air force flyers and cadet applicants during approximately 48 seconds of ecg 0.78% (952 males) had pvc within all age groups, but with increased incidence with increasing age. ventricular ectopy is more prevalent in men than in women of the same age data from large, population-based studies indicate that the prevalence is less for young white women without heart disease and greater for older african american individuals with hypertension.