<unk> s are harmless, but frequent<unk> s may increase the risk of developing cardiomyopathy, which can greatly impair heart function. On a more serious and severe scale, very frequent<unk> s can accompany underlying heart disease. People who do not have heart disease (with ejection fractions greater than 40%) have the same long-term prognoses as the minorance of people without<unk> s on the 24 hours. Emerging data also suggest that very frequent<unk>  ectopy may be associated with cardiomyopathy through a mechanism thought to be similar to that of chronic right<unk>  pacing associated cardiomyopathy. For patients with underlying chronic structural heart disease and complex ectopy, mortality is significantly increased. In meta-analysis of 11 studies, people with frequent<unk> s had risk of cardiac death twice as great as that of participants with occasionally<unk> s. Although most researchers attempted to exclude high-risk subjects, such as those with histories of cardiovascular disease, they did not test participants for underlying structural heart disease. In a study of 239 people with frequent<unk> s and without structural heart disease (i.e. in the presence of normal heart function) there were no cardiac events through 5.6 years on average, but there was correlation between<unk>  prevalence and decrease of ejection fraction and increase of left<unk>  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 and complex<unk> s 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<unk> s in healthy people were associated with a twofold increase in the risk of myocardial infarction. 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 criticised 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<unk>  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<unk> s. It is possible that<unk> s 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 very frequent<unk> s had an increased risk of heart failure 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<unk>  during a 10-second recording had triple the risk of atrial fibrillation of those without<unk> s, 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<unk>  (>20%) by antiarrhythmic drugs or by catheter ablation significantly improves heart performance. Recent studies have shown that those subjects with extremely frequent<unk> s (several thousand a day) can develop dilated cardiomyopathy. In these cases, if the<unk> s are reduced or removed (for example, via ablation therapy) the cardiomyopathy regresses.
Premature ventricular contraction
Premature atrial contraction
Benign early repolarization
Pre-excitation syndrome
Ectopic beat
Ectopic pacemaker
Premature junctional contraction
Drug-induced QT prolongation