Predictors of Recurrence of AF in Patients After Radiofrequency Ablation.

Catheter ablation is a well-known treatment for patients with AF. Despite the growing knowledge in the field, the identification of predictors of recurrence of AF after catheter ablation is one of the primary goals and is of major importance to improve long-term results of the procedure. The aim of this article is to provide an overview of what has been published in recent years and to summarise the major predictors, helping cardiac electrophysiologists in the selection of the right candidates for catheter ablation.

Evaluation of the SCHILLER BR-102 plus noninvasive ambulatory blood pressure monitor according to the International Protocol introduced by the Working Group on Blood Pressure Monitoring of the European Society of Hypertension.

OBJECTIVE: To evaluate the SCHILLER BR-102 plus (Schiller AG, Baar, Switzerland) noninvasive ambulatory blood pressure recorder according to the International Protocol for validation of blood pressure measuring devices in adults introduced by the Working Group on Blood Pressure Monitoring of the European Society of Hypertension. METHOD: One SCHILLER BR-102 plus blood pressure recorder was tested by a validation team, consisting of three persons: two observers (nurses) and a doctor, acting as supervisor and 'expert'. The European Society of Hypertension International Protocol comprises two phases. Fifteen participants were recruited for the first phase and, following a successful test, a further 18 persons (giving a total of 33) were recruited additionally. For phase 1, five of the 15 participants had systolic blood pressure and diastolic blood pressure in each of the ranges: low, medium and high. For phase 2, 11 of the 33 participants (including the first 15 participants) had systolic blood pressure and diastolic blood pressure in each of the ranges. The mercury standard for validation was preferred over the optional Sphygmocorder. Because the SCHILLER BR-102 plus has the oscillometric method as backup to the basic auscultatory measurement, both systems of measurement were subjected to individual validations. RESULTS: Results obtained show that the SCHILLER BR-102 plus noninvasive ambulatory blood pressure recorder meets all the requirements specified in the International Protocol for both oscillometric and auscultatory methods. CONCLUSION: On the basis of these results, the SCHILLER BR-102 plus can be recommended for ambulatory blood pressure measurement in clinical practice using both auscultatory and oscillometric modes.

Normal and abnormal circadian profiles of heart autonomic balance, evaluated by time-related common indicator of heart rate variability.

OBJECTIVE: Heart rate variability (HRV) is an universally accepted method for assessing the heart autonomic balance (HAB). At the same time HRV is a highly specific method, but with a low sensitivity to the cardiovascular diseases (CVD). We found that HRV indices may be applied to obtain differentiated characteristics of the HAB for individual CVD. METHODS: We assessed the changes taking place in the circadian characteristic of the autonomic balance, which has a definite profile with and without the principal CVD. We proposed adequate time-related autonomic balance indicator (TRABI) for evaluating the changes in the circadian nature of HAB by comparing the values of the HRV indices during rest and upon vegetative nervous system stimulation during two intervals in the 24-hour period in which there is a physiologically determined difference in the balance. RESULTS: The normal circadian characteristic of HAB is distinguished by a slight prevalence of the circadian nature of the parasympathetic component. The mean value of the assessments of the HRV indices using TRABI in healthy individuals, according to data from the study during rest and with the handgrip test is 0.100, according to data from the study during rest and with the Valsalva maneuver is 0.141. The mean values of the scores of the indices for HRV using TRABI in the comparative studies during rest and with the two stimulation tests are accordingly: with hypertension- 0.132 and 0.047; with morning myocardial infarction incidents- 0.177 and 0.107; with non-morning myocardial infarction incidents- 0.082 and 0.053. The patients with unstable angina in the population studied have a good long-term prognosis and the mean values in this case in the two comparative studies are 0.180 and 0.211. CONCLUSIONS: Cardiovascular diseases have a characteristic abnormal circadian nature of the autonomic balance. In our opinion, the proposed time-related autonomic balance indicator broadens, the opportunities for using HRV for HAB assessment. The method for evaluating the circadian changes in HAB through the HRV indices during rest and with stimulation during different time intervals is convenient and accessible for clinical use.

Possibilities of signal-averaged orthogonal and vector electrocardiography for locating and size evaluation of acute myocardial infarction with ST-elevation.

OBJECTIVE: The signal-averaged electrocardiography (SAECG) is known to be a useful tool for extraction and analysis of low-amplitude signal components. We found SAECG may be useful for precise location of the site of the myocardial necrosis and assessment of the severity of impaired left ventricular systolic function of patients with ST-elevation myocardial infarct (STEMI) in the acute phase. METHODS: High-resolution (1 MHz) ECG from 3 groups were collected: healthy controls (20), patients with anterior (17) and inferior STEMI (21). The three orthogonal leads X, Y, Z were synthesized from the 12 standard leads by known transformation. Synchronized averaging was carried out over hundred P-QRS-T intervals of each orthogonal lead. The resulting intervals of all subjects within a group were additionally averaged. The obtained X, Y and Z patterns, as well as the derived loops in the vectorcardiographic planes (VCG patterns) were studied for significant divergences. RESULTS: The summarized analysis presenting the possibilities of QRS- and T-vector indicators for correct classification of patients with STEMI shows that the determined discriminators classify correctly 91.4% of the examined patients. The optimized set of QRS-vector indicators for discrimination between healthy controls and patients with inferior STEMI include angle alpha of the maximal vector in both the sagittal and the horizontal plane. These two indicators show as high predictive value as all QRS-vector indicators -82.9%. The optimized combination of QRS-vector indicators for discrimination between healthy controls and patients with anterior STEMI includes amplitude of the maximal vector in the frontal and sagittal planes, angle alpha of the maximal vector in the sagittal plane and the area of the loop in the frontal plane. This optimized combination has a common mean percentage of correctly classified patients of about 91.9%. The accuracy for infarct zone localization is improved with optimized combinations involving together QRS- and T-vector indicators. The achieved common mean percentages of correct classifications are 94.6% (healthy controls-anterior STEMI), 92.7% (healthy controls-inferior STEMI) and 97.4% (anterior STEMI-inferior STEMI). The set of all QRS-and T-vector indicators of patients with anterior STEMI regarding 2D-echocardiographic ejection fraction shows very high correlation coefficient, reaching about 0.99. In contrast, we did not find significantly high correlation in patients with inferior STEMI. CONCLUSIONS: Both the signal-averaged orthogonal ECG and the synthesized on its basis VCG show markedly high sensitivity regarding location of ST-elevation myocardial infarct. The possibility for facilitated and fast performance of this examination in clinical conditions, including emergency, the lack of necessity of specially trained staff for carrying out the examination and interpretation of the results, as well as the very low prime cost, make this electrophysiological method very suitable for application in the routine clinical practice for qualitative and quantitative assessment of patients with acute coronary syndromes.

Transthoracic impedance study with large self-adhesive electrodes in two conventional positions for defibrillation.

External defibrillation requires the application of high voltage electrical impulses via large external electrodes, placed on selected locations on the thorax surface. The position of the electrodes is one of the major determinants of the transthoracic impedance (TTI) which influences the intracardiac current flow during electric shock and defibrillation success. The variety of factors which influence TTI measurements raised our interest to investigate the range of TTI values and the temporal TTI variance during long-term application of defibrillation self-adhesive electrodes in two conventional positions on the patient's chest--position 1 (sub-clavicular/sub-axillar position) and position 2 (antero-posterior position). The prospective study included 86 randomly selected volunteers (39 male and 49 female, 67 patients with normal skin, 13 patients with dry skin and 6 patients with greasy skin, 16 patients with chest pilosity and 70 patients without chest pilosity). The TTI was measured according to the interelectrode voltage drop obtained by passage of a low-amplitude high-frequency current (32 kHz) between the two self-adhesive electrodes (active area about 92 cm2). For each patient, the TTI values were measured within 10 s, 1 min and 5 min after sticking the electrodes to the skin surface, independently for the two tested electrode positions. We found that the expected TTI range is between 58 Omega and 152 Omega for position 1 and between 55 Omega and 149 Omega for position 2. Although the two TTI ranges are comparable, we measured significantly higher TTI mean of about (107.2 +/- 22.3) Omega for position 1 compared to (96.6 +/- 19.2) Omega for position 2 (p = 0.001). This fact suggested that the antero-posterior position of the electrodes is favourable for defibrillation. Within the investigated time interval of 5 min, we observed a significant TTI reduction with about 6.9% (7.4 Omega/107.2 Omega) for position 1 and about 5.3% (5.1 Omega/96.6 Omega) for position 2. We suppose that the long-term application of self-adhesive electrodes would lead to improvement of the physical conditions for conduction of the defibrillation current and to diminution of energy loss in the electrode-skin contact impedance. We found that gender is important when position 1 is used because women have significantly higher TTI (111 +/- 20.3) Omega compared to the TTI of men (102.6 +/- 24) Omega (p = 0.0442). Although we found some specifics of the electrode-skin contact layer, we can conclude that because of the insignificant differences in TTI, the operator of the defibrillator paddles does not need to take into consideration the skin type and pilosity of the patients. Analysis of the correlations between TTI and the individual patient characteristics (chest size, weight, height, age) showed that these patient characteristics are unreliable factors for prediction of the TTI values and optimal defibrillation pulse parameters and energy.

Diagnostic value of the RR-variability indicators for mild hypertension.

Experimental and clinical studies have shown that an imbalance of the cardiovascular system autonomous regulation can lead to complications. In this study we have aimed to investigate whether the vegetative control of patients with mild hypertension is disturbed and to evaluate the power of the RR-variability indicators to detect the disturbances. RR variability has been studied in two groups of individuals: normotensive and mildly hypertensive. The indicators of the heart rate variability (HRV) from the 'Cardiovit CS-100 ECG Module' electrocardiograph have been used. The HRV is known to exhibit circadian variations, therefore RR intervals were recorded in two separate sessions: morning (8-9 am) and afternoon (2-3 pm). Each session included three tests: in a resting state, with a handgrip test and with the Valsalva manoeuvre. The multivariate statistical method was applied separately to the morning and afternoon data. A number of classification algorithms were synthesized, yielding correct recognition of normotensive and mildly hypertensive subjects of 91.9% and 94.2% for the morning and afternoon sessions, respectively. We have thoroughly discussed the substantiating reasons for the high statistical significance and reliability of the discrimination obtained. The high sensitivity and specificity of the RR-variability indicators included in the classification models suggest correlative changes of the nervous system vegetative balance in mildly hypertensive patients. The results of the study show the possibility for statistically significant diagnosis of mild hypertension, for prediction of ventricular arrhythmia, left ventricular hypertrophy and ischaemic heart disease.