Repeatability of Sleep Apnea Detection in 48‐Hour Holter ECG Monitoring

Background: There is a significant relationship between obstructive sleep apnea (OSA) and cardiovascular diseases. Reliability of new methods evaluating apnea in Holter ECG monitoring is still the matter of investigators’ studies. Methods: In 48‐hour Holter ECG monitoring recordings of 63 patients, we assessed repeatability, comparing the results from both sleep periods. Results: We found good repeatability in evaluation of apnea‐hypopnea index value. There was moderate agreement in three categories, that is, normal or bordeline or apneic assignment. Assignment to “healthy” (normal and borderline) or apneic subgroup during consecutive sleep periods showed high repeatability. Conclusions: Holter ECG monitoring is a repetitive method of preliminary diagnosis in patients evaluated for sleep apnea syndrome. Ann Noninvasive Electrocardiol 2010;15(3):218–222     

Variables affecting the change in systemic blood pressure in response to nasal CPAP in obstructive sleep apnea patients

We hypothesized that an improvement in systemic blood pressure (BP) during continuous positive airway pressure (CPAP) treatment of obstructive sleep apnea (OSA) would be related to severity of hypertension (HTN), morphometric parameters such as body mass index, and level of CPAP adherence. We tested this hypothesis with a retrospective review of 85 consecutive OSA patients who had completed diagnostic and CPAP titration polysomnograms and were equipped with a CPAP-adherence monitoring system for a minimum of 1 month of observation. Sphygmomanometer-obtained BP readings were compared at baseline and after 4–6 weeks of CPAP therapy. Presentation BP was significantly and strongly associated with the change in BP seen with treatment. Those with an elevated systolic and diastolic BP and those with an elevation of either systolic or diastolic BP showed a significant fall in BP on CPAP. Those with a BP below the hypertensive range of 140/90 on presentation did not have a significant drop in BP with CPAP. There were no significant changes in systolic, diastolic, or mean BP when patients were categorized by the severity of HTN, as determined by the number of antihypertensive medications prescribed or if they were categorized by the degree of CPAP adherence, objectively determined by the average use of more or less than 4 h/night. We conclude that HTN at initial presentation is among the most important indicators of potential benefit of CPAP administration on BP.     

Ventricular arrhythmias during 24-h ambulatory ECG recording: incidence, risk factors and prognosis in men with and without a history of cardiovascular disease

Abstract. Engström G, Hedblad B, Janzon L, Juul-Möller S (Malmö University Hospital, Malmö, Sweden). Ventricular arrhythmias during 24-h ambulatory ECG recording: incidence, risk factors and prognosis in men with and without a history of cardiovascular disease. J Intern Med 1999; 246: 363–372. Objective. To study incidence, prognosis and risk factors of ventricular arrhythmias in men with and without asymptomatic non-invasively detected cardiovascular disease (CVD). Design. Prospective cohort study with 11 years’ follow-up. The subjects went through 24-h ambulatory electrocardiographic (ECG) registrations and non-invasive examinations of leg and carotid arteries at the baseline examination. Setting. Malmö, Sweden. Subjects. Four hundred and forty-three randomly selected 68-year-old men. Main outcome measures. Mortality and cardiac event rates during an 11-year period. Results. Frequent or complex arrhythmias (Lown class 2–5) were common in men both with and without CVD. However, the associated prognoses were different. In men with CVD, frequent or complex arrhythmias were associated with increased cardiac event rates (P = 0.001) and increased mortality (P = 0.054). This pattern was also found in men with asymptomatic leg and carotid artery disease, although the frequency of arrhythmia in Lown class 2–5 was similar to that in men without CVD. Men with angina pectoris or previous myocardial infarction in combination with leg or carotid artery disease had the most arrhythmias and the worst prognosis. No relationship between frequent or complex arrhythmias and mortality or cardiac events was found in men without CVD. In a logistic regression, smoking and diabetes mellitus were significant and independent determinants of frequent or complex arrhythmias in men with CVD. High alcohol consumption was associated with arrhythmias in men without CVD. Conclusion. Ambulatory ECG recording is a feasible method to improve risk assessment in men with CVD. In this group, frequent or complex arrhythmias are associated with smoking and diabetes mellitus.     

Effects of β-Blocker Therapy on the Dynamic QT/RR Relation in Patients with Long QT Syndrome During 24-Hour Holter ECG Monitoring

Objective: Patients with long QT syndrome (LQTS) have an abnormality in the dynamic relationship between the QT and RR intervals (QT/RR relation) assessed by 24-hour Holter ECG monitoring. The clinical efficacy of β-blocker therapy in LQTS patients has been established, but its antiarrhythmic mechanism has not been fully elucidated. In the present study, the influences of β-blocker therapy on the QT/RR relation were investigated in LQTS patients with no arrhythmic event during β-blocker therapy. Methods: Holter ECG recordings before and after the therapy were obtained from seven LQTS patients (all female, age range 10–45 years). The QT/RR relation was analyzed by our original computer algorithm with automatic measurement of the Q-aT interval (time interval from the QRS onset to the T wave apex. The correlation coefficient (r), and the slope of the best fit linear regression line between the Q-aT and RR intervals (Q-aT/RR slope) after β-blocker therapy were compared with those before the therapy. To determine whether the dose of β-blockers was sufficient for suppression of the sympathetic nervous activity, a frequency-domain analysis of the heart rate variability was performed (low frequency power [LF]: 0.04–0.15 Hz, high frequency power [HF]: 0.15–0.40 Hz). Results: The LF component of the heart rate variability decreased and the HF component increased during the daytime after β-blocker therapy. However, the Q-aT/RR relation after β-blocker therapy was the same as that before the therapy (mean slope before = 0.20 ± 0.07, mean slope after = 0.19 ± 0.08; P = not significant; mean r before = 0.82 ± 0.17; mean r after = 0.76 ± 0.15; P = not significant). Conclusion: β-Blocker therapy did not affect the unique Q-aT/RR relation, which reflects an intrinsic abnormality of the ventricular repolarization in LQTS patients.