R/S Ratio Variability in Lead V1 Observed between Selected Four 1-Minute ECG Fragments of 24-Hour ECG as a Predictor of Incomplete Resynchronization during Full 24-Hour ECG: Pilot Study.

BACKGROUND: About 30% of patients do not have an effective cardiac resynchronization therapy (CRT). Routine assessment of CRT by devices interrogation (DI) is not entirely reliable. Additional information provide detailed QRS analysis in 24-hour ECG, however it is time-consuming. The aim of the study was the assessment of R/S ratio variability in lead V1 between selected fragments of 24-hour ECG as a predictor of incomplete biventricular pacing (BIVP) during full 24-hour ECG. METHODS: The 12-lead 24-hour ECGs of 43 patients with sinus rhythm were studied. During 24-hour ECG the 6-minute walk test (6MWT) was performed. The CRT was assessed by analyzing DI and full 24-hour ECG and four 1-minute fragments of these ECG recordings: during the minimum and the maximum heart rate and at the 1st and last minute of 6MWT. RESULTS: During DI the effective (>95%) BIVP was present in 36 patients (83.7%). Analysis of full 24-hour ECG confirmed appropriate BIVP in 31 patients (72%) and suspected incomplete BIVP (≤95%) in 12 patients (28%). In 9/12 patients the R/S ratio variability in lead V1 was visible between selected ECG fragments of 24-hour ECG. These results were not associated with the results of DI but were significantly associated with full 24-hour analysis of QRS. CONCLUSIONS: R/S variability in lead V1 between selected fragments of 24-hour ECG can be considered a predictor of potentially incomplete BIVP confirmed by further complete 24-hour ECG analysis in patients with appropriate pacing reported during DI.

Analysis of the QRS morphology in lead V1 during 24-hour Holter electrocardiogram monitoring to evaluate function of a cardiac resynchronisation therapy device in patients with sinus rhythm: a pilot study.

BACKGROUND: Cardiac resynchronisation therapy (CRT) is an important advance in the treatment of chronic heart failure. The aim of CRT is biventricular capture in all beats. However, inadequate delivery of biventricular pacing is still seen in about 30% of patients with an implanted CRT device. Device interrogation is a routine approach to assess CRT delivery. However, some reports indicate that analysis of 24-h electrocardiogram (ECG) may provide additional and important information regarding CRT function. AIM: Assessment of the adequacy of CRT delivery based on device interrogation and analysis of QRS morphology during 24-h ECG recording in patients with preserved sinus rhythm (SR). METHODS: We analysed 24-h Holter ECG recordings and data from device interrogation devices in 43 patients with preserved SR (age 56 ± 23 years, 9 women and 34 men). The obtained results were compared in an independent manner. Assessment of adequacy of CRT delivery by 24-h ECG was based on the occurrence of QRS variability, defined as a change in R wave amplitude in lead V1 by > 3 mm and/or change in QRS duration by > 40 ms and/or change in the R/S ratio. Adequate CRT delivery, i.e. complete resynchronisation, was defined as more than 95% of pacing without the defined QRS variability. RESULTS: Both methods allowed independent assessment of CRT delivery (p < 0.05 by the Fisher's exact test). In multivariate analysis, factors that were independently associated with incomplete resynchronisation included ventricular arrhythmias (each 100 ventricular beats per day increased the risk of incomplete resynchronisation 1.14-fold; confidence interval [CI] 1.036-1.25, p = 0.007), maximum heart rate (HR) (each increase by 10 bpm increased the risk 3.3-fold; CI 1.36-7.9, p = 0.008), QRS duration at the minimum HR (each increase by 10 ms increased the risk 1.74-fold; CI 1.075-2.8, p = 0.024), and the programmed atrioventricular delay (each increase by 10 ms increased the risk 2.15-fold, CI 1.18-3.9, p = 0.013). CONCLUSIONS: In patients with preserved SR, device interrogation and evaluation of 24-h ECG are complementary methods to evaluate adequate CRT delivery. Therefore, both methods should be taken into account when assessing CRT function.

Influence of warm­up ischemia on the effects of exercise training in patients with stable angina.

INTRODUCTION:  It is still unknown whether ischemia­inducing training in patients with stable angina is superior to the training conducted below the ischemic threshold (IT) according to the current guidelines. OBJECTIVES:  The aim of the study was to assess the influence of warm­up ischemia prior to training on the effects of training conducted either at or below the IT in patients with stable angina. PATIENTS AND METHODS:  Thirty male patients aged 56 ±8 years, after myocardial infarction, with stable angina and positive exercise test (ET1) were divided into 2 groups: group A included 18 patients with the warm­up effect, group B - 12 patients without this effect. All patients followed an 8­week interval training program (TP). The intensity of training was planned to reach the heart rate at the IT. Successive ETs were performed immediately after the TP (ET2), at day 3 (ET3), day 10 (ET4), and at 1 month (ET5).   RESULTS:  After the TP, there was a statistically significant improvement in group A in all analyzed variables except maximum ST depression (max STD). Maximal workload increased by 28%, walking distance by 24%, duration by 20%, and time to 1­mm STD by 28%. Max STD reduction amounted to 14% (P =0.13). The beneficial effect of training on exercise­induced ischemia was maintained for up to 10 days (ET4) and on physical capacity for up to 1 month (ET5). In group B, the TP did not affect time to 1­mm STD, but physical capacity improved significantly and was maintained for up to 1 month (ET5). CONCLUSIONS:  The warm­up effect appears to be necessary to attenuate myocardial ischemia after training.