The impact of hemodialysis on the dispersion of ventricular repolarization.

BACKGROUND: Sudden cardiac death is prevalent in chronic hemodialysis (HD) patients while the dialysis process may have arrhythmogenic potential. We sought to examine the effect of HD on conventional electrocardiographic parameters as well as on novel indexes of repolarization, given that increased spatial dispersion of repolarization is related to ventricular arrhythmias. METHODS: We recorded clinical, echocardiographic, and laboratory parameters as well as electrocardiographic indexes before and after a single HD session. Specifically, we calculated the QTc interval, the QRS duration, the T peak-to-end (Tpe) interval, and the Tpe/QT ratio. RESULTS: The study population consisted of 66 chronic HD patients (mean age: 68.9 ± 11.8 years, 40 males). Heart rate, blood pressure, QRS duration, QTc interval, and QT dispersion did not change significantly after the HD session. However, the Tpe interval and the Tpe/QT ratio increased significantly (80 [65-90] ms vs 85 [77.5-100] ms; P = 0.04, and 0.21 [0.18-0.24] vs 0.25 [0.21-0.28]; P = 0.05, respectively). Correlation analysis and multiple regression analysis failed to show significant associations between the baseline parameters and the baseline values of Tpe and Tpe/QT or between the change of the laboratory parameters during HD and the corresponding change of the Tpe and the Tpe/QT values. No significant arrhythmias were observed during the HD sessions. CONCLUSIONS: HD induces an increase in novel markers of spatial dispersion of ventricular repolarization. Whether the assessment of these indexes of heterogeneity of repolarization at baseline or their change during HD has a prognostic value with regard to future untoward events, remains to be elucidated.

Persistent smokers after myocardial infarction: a group that requires special attention.

BACKGROUND: Despite the detrimental effects of smoking on the cardiovascular system, a significant number of patients with coronary heart disease continue to smoke. We aimed to record compliance to medication and attitude towards recommended lifestyle changes in patients who suffered from myocardial infarction (MI) and continued to smoke after the coronary event. METHODS: A total of 1011 consecutive patients (<75 years) with a history of MI (>6 months) were recruited during the period 2000-2003 from the outpatient cardiology clinic of a district general hospital. All patients were interviewed and blood was taken for lipid measurements. Glycosylated haemoglobin (HbA(1 c)) was also measured in all diabetics. RESULTS: Three hundred and twenty-nine (32.5%) patients reported smoking at interview, while 338 (33.5%) were ex-smokers of whom 278 (45.8% of all smokers) had quit smoking after MI and 344 (34%) had never smoked. Persistent smokers had significantly lower high-density lipoprotein cholesterol levels than nonsmokers (1.03+/-0.28 vs. 1.09+/-0.29 mmol/l, p=0.001). Persistent smokers with diabetes had poorer glycaemic control than nonsmoker diabetic patients as indicated by HbA(1c) levels (8+/-1.7% vs. 7.2+/-1.3%, p=0.001). Fewer persistent smokers were taking hypolipidaemic drugs than nonsmokers (31% vs. 40.3%, p=0.005). Finally, persistent smokers were less frequently performing regular exercise than nonsmokers (42% vs. 51%, p=0.008). CONCLUSIONS: Patients who remain smokers after MI have a more negative attitude towards health aspects, are less compliant with their medications, and therefore constitute a high-risk subgroup, which requires special attention and should be professionally encouraged and supported to stop smoking.