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Biomedical subjects

P Kulakowski

Publications and source records attributed to P Kulakowski.

At least 19 recordsLinked to original sources
PubMed2001

Extrasystolic beats affect transmural electrical dispersion during programmed electrical stimulation.

BACKGROUND: Experimental studies suggest that the electrocardiographic Tpeak-Tend (TpTe) interval reflects transmural dispersion of repolarization (TDR). The genesis and role of the TpTe interval in a clinical setting have not been established. This study aimed to assess the clinical usefulness of the TpTe interval as an index of TDR and a pro-arrhythmic marker. MATERIALS AND METHODS: Endocardial monophasic action potential (MAP) duration and electrocardiographic QTp, QTe and TpTe intervals were assessed in 13 patients undergoing an electrophysiological study. Surface electrocardiograms were recorded during right ventricular pacing (Basic Cycle Length = 600 ms) before and after single extrastimuli. RESULTS: Ventricular arrhythmia was induced in six patients. During ventricular pacing, MAP duration and QTp intervals shortened in response to extrastimuli applied at progressively shorter coupling intervals. In contrast, QTe intervals increased in response to premature stimulation and QTe dispersion increased at short coupling intervals. During sinus rhythm, the TpTe interval was greater in the inducible group in leads V3-V4. Premature stimulation increased the duration of TpTe intervals, suggesting an increase in TDR. The maximum TpTe interval was greater in the inducible than in the noninducible group, both during baseline ventricular drive pacing (163 +/- 22 vs. 130 +/- 27 ms, respectively, P < 0.03) and after application of shortly coupled extrastimuli (263 +/- 66 vs. 200 +/- 47 ms, respectively, P < 0.05). CONCLUSIONS: The TpTe interval of surface ECG is likely to represent TDR. TDR is increased by premature ventricular stimulation and the magnitude of the maximum TpTe interval (i.e. maximum TDR) during ventricular pacing is greater in patients with inducible arrhythmias.

Action Potentials↗
PubMed2001

Efficacy and safety of dofetilide in the prevention of symptomatic episodes of paroxysmal supraventricular tachycardia: a 6-month double-blind comparison with propafenone and placebo.

BACKGROUND: Existing drug therapies for paroxysmal supraventricular tachycardia (PSVT) have potentially serious adverse effects. Dofetilide, a pure class III antiarrhythmic agent, may offer an effective and safe alternative for treating PSVT. This study compared the efficacy and safety of dofetilide with that of propafenone and placebo in the prevention of PSVT. METHODS: This multicenter, randomized, placebo-controlled, parallel-group study compared the effectiveness of oral dofetilide 500 microg given twice daily with that of propafenone 150 mg given 3 times a day and placebo in preventing the recurrence of PSVT in 122 symptomatic patients. Episodes of PSVT were documented by symptom diaries and Hertcard (Hertford Medical, Hertfordshire, UK) event recorders. RESULTS: After 6 months of treatment, patients taking dofetilide, propafenone, and placebo had a 50%, 54%, and 6% probability, respectively, of remaining free of episodes of PSVT (P <.001 for both dofetilide and propafenone vs placebo). Both dofetilide and propafenone also decreased the frequency of episodes of PSVT; the median numbers of episodes in the dofetilide- and propafenone-treated groups were 1 and 0.5, respectively, compared with 5 in the placebo-treated group. Dofetilide was well tolerated; no proarrhythmia occurred. Three patients taking propafenone had serious treatment-related adverse effects that required drug discontinuation. CONCLUSIONS: Dofetilide and propafenone were equally effective in preventing the recurrence of or decreasing the frequency of PSVT.

Administration, Oral↗
PubMed1998

Wavelet decomposition analysis of the signal averaged electrocardiogram used for risk stratification of patients with hypertrophic cardiomyopathy.

AIMS: To study the predictive value of wavelet decomposition, as demonstrated by the signal-averaged ECG, in order to identify patients with hypertrophic cardiomyopathy at increased risk for malignant ventricular arrhythmias or sudden death. METHODS AND RESULTS: Two hundred and forty-six patients with hypertrophic cardiomyopathy were studied. During a mean follow-up of 68 +/- 17 months 32 patients died, of whom 17 died suddenly. Patients with sudden death, together with eight patients with a history of ventricular fibrillation (sudden death/ventricular fibrillation group) were analysed and compared to the other 221 patients as well as to a subgroup of 82 patients without a history of syncope, ventricular arrhythmias on a long-term ECG recording or a family history of sudden death. There were no differences in mean values of the four wavelet decomposition parameters among patients in the sudden death/ ventricular fibrillation group, those without sudden death/ ventricular fibrillation or patients in the low risk group. There were, however, significant differences between patients dying non-suddenly and patients being alive at the end of follow-up. Eighty-seven patients (35%) demonstrated evidence of non-sustained ventricular tachycardia on a long-term ECG. Analysis of wavelet decomposition resulted in abnormal findings in these patients more often than in those without ventricular arrhythmias. CONCLUSION: The usefulness of wavelet decomposition analysis in predicting sudden death or ventricular fibrillation is limited in patients with hypertrophic cardiomyopathy. It may, however, play a role in identifying patients at risk of dying non-suddenly and of patients with non-sustained ventricular tachycardia.

Adolescent↗
PubMed1998

Use of spectral turbulence analysis for the identification of patients at high risk for ventricular fibrillation and sudden death in patients with hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy carries an increased risk of sudden death. The aim of the present study was to assess the predictive value of the signal-averaged ECG, analysed in the time domain and using a new method, spectral turbulence analysis, for the identification of high-risk patients. Two-hundred and forty-six patients with hypertrophic cardiomyopathy were studied. During a mean follow-up of 68 +/- 17 months, 17 patients died suddenly. Patients with sudden death (SD) and/or a history of ventricular fibrillation (VF; n = 25) were compared to patients without SD/VF (n = 221) and to patients without any recognised risk factors for SD (n = 82). There were no differences in mean values of the time domain or spectral turbulence parameters analysed between patients in the SD/VF group and the patients without SD/VF or in the low-risk group. It is concluded that the clinical usefulness of the signal-averaged ECG, analysed in the time domain or as spectral turbulence analysis, is limited in identifying high-risk patients with hypertrophic cardiomyopathy.

Adult↗
PubMed1996

The incidence of asymptomatic paroxysmal atrial fibrillation in patients treated with propranolol or propafenone.

Anti-arrhythmic therapy for paroxysmal atrial fibrillation leads to complete symptomatic relief in a number of patients. The elimination of symptoms may be associated either with a complete elimination of arrhythmia or with a conversion of symptomatic atrial fibrillation into asymptomatic episodes of arrhythmia. The aim of the study was to evaluate the occurrence of asymptomatic paroxysmal atrial fibrillation in 52 patients treated with propafenone (35 drug trials) or propranolol (34 drug trials) by means of ambulatory ECG Holter monitoring. Propafenone was clinically effective (complete relief of symptoms) in 26 (74%) patients. However, in 7 cases (27%) asymptomatic episodes of arrhythmia were still recorded when awake. In patients treated with propranolol clinical symptoms were absent in 18 (53%). However, in 4 (22%) patients attacks of paroxysmal atrial fibrillation were present. The mechanism of drug-induced conversion of symptomatic episodes of atrial fibrillation into asymptomatic spells of arrhythmia was a marked shortening in duration of episodes in 7 patients (from 2215 +/- 3843 s to 16 +/- 10 s, N.S.) or by a significant slowing of ventricular response during atrial fibrillation in 4 patients (from 125 +/- 27 to 84 +/- 8 beats/min, P = 0.05). In conclusion, in a significant proportion of patients with symptomatic paroxysmal atrial fibrillation asymptomatic episodes of arrhythmia may occur while on anti-arrhythmic drug therapy. Some of these patients, particularly those with other risk factors for stroke such as advanced age or the presence of organic heart disease, may require anti-coagulant therapy or change in anti-arrhythmic treatment, and can be selected on the basis of ambulatory ECG monitoring.

Aged↗
PubMed1996

Nifedipine and captopril exert divergent effects on heart rate variability in patients with acute episodes of hypertension.

Acute changes of heart rate variability (HRV) depict alterations in autonomic influences on cardiovascular system and often precede ventricular arrhythmias. The aim of the study was to assess effects of sublingual 10 mg nifedipine (n = 15) or 25 mg captopril (n = 13) on HRV in consecutive patients admitted to hospital due to severe hypertension. HRV was calculated on-line from 300 cardiac cycles before and 60-90 min after drug administration. At baseline systolic blood pressure (SBP) was > 190 mm Hg and/or diastolic blood pressure (DBP) > 110 mm Hg. Both agents caused similar reduction of blood pressure (BP). Nifedipine reduced variance (-63 +/- 6%; P < 0.0001) and high-frequency (HF) component (-72 +/- 8%; P < 0.0001), and increased both LF/HF ratio (+870 +/- 336%; P < 0.02) and heart rate (+14 +/- 3%; P < 0.0001). Captopril exerted different effects: variance and HF component increased by +176 +/- 55%; (P < 0.007) and +126 +/- 44% (P < 0.015), respectively. LF/HF (low/high frequency) ratio decreased (-44 +/- 19%; P < 0.04) together with heart rate (-4 +/- 1%; < 0.009). It is concluded that captopril, in contrast to nifedipine, increases HRV and decreases LF/HF ratio and therefore is a better choice in hypertensive patients who might be prone to dangerous arrhythmias.

Acute Disease↗
PubMed1995

Influence of the infarct site on the identification of patients with ventricular tachycardia after myocardial infarction based on the time-domain and spectral turbulence analysis of the signal-averaged electrocardiogram.

In a significant proportion of patients with sustained ventricular tachycardia (VT) following anterior myocardial infarction, the areas of slow conduction are activated early during cardiac depolarization. Therefore, they may not be detected by the standard time-domain analysis of the signal-averaged electrocardiogram (SAECG) which is limited to the terminal part of the QRS complex. Spectral turbulence analysis of the SAECG is a new frequency domain technique which examines the whole QRS complex and may improve identification of patients with sustained VT following anterior infarction. We compared the results of time-domain and spectral turbulence analyses of the SAECG in 53 postinfarction patients with sustained VT and in 53 age-, gender- and infarct site-matched patients without VT. The receiver operator characteristic curves have shown that the time-domain analysis resulted in better identification of patients with VT following inferior than following anterior infarction (e.g., at the sensitivity level of 90%, the corresponding values of specificity were 96 and 90%, respectively), whereas the spectral turbulence analysis performed better in the anterior site of infarction. When both time-domain and spectral turbulence analyses were combined, the accuracy of the SAECG for identification of patients with VT following anterior infarction improved, reaching a specificity of 97% at the sensitivity level of 90%. In conclusion (1) spectral turbulence analysis of the SAECG results in better identification of patients with VT following anterior than following inferior infarction, and (2) the combination of time-domain and spectral turbulence analyses of the SAECG may improve identification of patients with VT following anterior infarction.

Aged↗
PubMed1994

Spectral turbulence analysis versus time-domain analysis of the signal-averaged ECG in survivors of acute myocardial infarction.

This study compared the time-domain and spectral turbulence analyses of signal-averaged electrocardiogram (ECG) for the prediction of risk after acute myocardial infarction. Signal-averaged ECGs were recorded in 553 survivors of acute myocardial infarction before hospital discharge. The study excluded cases with bundle branch block and other conduction abnormalities, and patients were followed for at least 1 year. During the first year of the follow-up period, 30 patients died and 20 presented with ventricular tachycardia/fibrillation. The signal-averaged ECG recordings were analyzed using conventional time domain at 40-250 Hz and spectral turbulence analyses. The indices provided by both types of analysis were compared in patients with and without endpoints. The optimum positive predictive characteristics were calculated for the prediction of all cause mortality and of ventricular tachycardia based on the time domain and on the spectral turbulence indices. Spectral turbulence analysis provided significantly lower positive predictive accuracy (14.5% at 40% sensitivity) than the time-domain analysis (26.7% at 40% sensitivity) for prediction of ventricular tachycardia/fibrillation during 1 year after infarction (P < .01). However, spectral turbulence analysis provided significantly higher positive predictive accuracy (27.2% at 30% sensitivity) than the time-domain analysis (16.9% at 30% sensitivity) for the prediction of 1-year all-cause mortality (P < .01). Thus, spectral turbulence analysis was inferior to the time-domain analysis in predicting ventricular tachycardia/fibrillation during the first year after myocardial infarction, but it was more powerful in predicting 1-year mortality.

Aged↗
PubMed1994

Influence of filtering techniques on the time-domain analysis, diagnosis, and clinical use of signal-averaged electrocardiogram.

In order to investigate the effect of different filtering techniques on the time-domain analysis of signal-averaged electrocardiogram (SAECG), recordings of 1,192 subjects were analyzed using Butterworth and Del Mar filters, both set at 40-250 Hz high and low pass frequencies. The recordings were taken from six clinically defined groups: (a) survivors of acute myocardial infarction (n = 553); (b) patients with sustained symptomatic postinfarction ventricular tachycardia (n = 89); (c) patients with hyperthropic cardiomyopathy (n = 219); (d) patients with dilated cardiomyopathy (n = 76); (e) direct relatives of patients with dilated cardiomyopathy (n = 170); and (f) normal healthy volunteers (n = 85). The study investigated differences between the SAECG results reported with both filters in three individual aspects: (1) numerical values of individual time-domain SAECG variables; (2) differences in SAECG findings of patients with postinfarction ventricular tachycardia and pair matched patients with uncomplicated follow-up after acute infarction; and (3) the power of SAECG findings to predict high risk of arrhythmic complication (sudden death and/or sustained ventricular tachycardia) among survivors of acute myocardial infarction. Compared with the Butterworth filter, the Del Mar filter led to a systematic difference of +8% in total QRS duration, was equally powerful in distinguishing between the pair matched patients with and without postinfarction ventricular tachycardia, and was statistically significantly more powerful in identifying those survivors of acute infarction who were at high risk of arrhythmic complications. The study concludes that the use of different filters may produce discordant results of SAECG analysis. Normal and abnormal values for various types of SAECG recording and analysis have to be established individually for different equipment and different software settings. These optimal cut-offs of SAECG variables should also take into account the clinical characteristics of patient groups.

Cardiomyopathy, Dilated↗
PubMed1994

Temporal influences on the prediction of postinfarction mortality by heart rate variability: a comparison with the left ventricular ejection fraction.

OBJECTIVE: To examine the influence of the duration of follow up on the values of heart rate variability (HRV) and the left ventricular ejection fraction (LVEF) for predicting mortality after infarction. BACKGROUND: HRV is an index of autonomic balance that identifies patients at a high risk of arrhythmic events. The index is most depressed during the first few weeks after myocardial infarction whereas left ventricular function tends to deteriorate with time. HYPOTHESIS: The value of depressed HRV measured before discharge from hospital for predicting mortality after infarction should decline with time. METHODS: The HRV and the LVEF were assessed in 433 survivors of a first acute myocardial infarction: HRV < 20 units and LVEF < 40% were taken as cut off points. Kaplan-Meier survival functions for total cardiac mortality and sudden cardiac death were calculated for the whole five year follow up period and for different intervening periods. RESULTS: During follow up of four weeks to five years there were 46 (10.6%) deaths and 15 (3.5%) patients died suddenly. Within the whole follow up period, HRV < 20 units and LVEF < 40% were both strongly associated with total cardiac mortality (p < 0.0001), but HRV was an independent predictor of total cardiac mortality only during the first six months of follow up. There were no deaths predicted by HRV < 20 units after the first year of follow up whereas LVEF < 40% had a sensitivity of 43% and a positive predictive accuracy of 9% for predicting death during this period. HRV < 20 units was better than LVEF < 40% in predicting sudden deaths during the first year of follow up but was an independent predictor only of those sudden deaths occurring within six months of infarction. CONCLUSIONS: The duration of follow up affects the prediction of sudden death and total cardiac mortality from HRV. Reduced HRV as measured before discharge from hospital does not seem to retain independent prognostic value after six months of follow up. These findings have potential implications for the serial evaluation of HRV and for the prevention of sudden death after myocardial infarction.

Death, Sudden, Cardiac↗
PubMed1993

Usefulness of signal-averaged electrocardiogram in idiopathic dilated cardiomyopathy for identifying patients with ventricular arrhythmias.

In idiopathic dilated cardiomyopathy (IDC), the relation between the signal-averaged electrocardiogram and ventricular tachycardia (VT) remains unclear. In this study, conventional time domain and frequency domain analyses (2-dimensional, spectral temporal mapping and spectral turbulence analysis) of the signal-averaged electrocardiogram were performed in 64 patients with IDC. Eight patients had a history of symptomatic sustained VT and an additional 24 had nonsustained VT recorded during ambulatory electrocardiography. Conventional time domain analysis, using the 25 and 40 Hz filter, and spectral temporal mapping, detected late potentials within the terminal QRS in 8 (13%), 14 (22%) and 18 (28%) patients, respectively. Late potentials were seen more often in patients with than without VT, and in patients with sustained versus nonsustained VT, but these differences were not significant. The predictive accuracy of these techniques in detecting either form of VT were: sensitivity, 22, 25 and 31%; specificity, 97, 81 and 75%; and overall predictive value, 59, 53 and 50%, respectively. Two-dimensional frequency domain analysis of the signal-averaged electrocardiogram revealed a higher energy and area ratio in patients with than without VT (entire QRS), and in patients with sustained versus nonsustained VT (entire QRS and terminal QRS). Spectral turbulence analysis was abnormal in 24 patients (39%), but no differences were observed between patients with and without VT. During follow-up (mean duration 18 +/- 14 months), 5 patients had arrhythmic events (3 died suddenly, 1 had aborted sudden death and 1 developed sustained VT).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Effects of procainamide on the signal-averaged electrocardiogram in relation to the results of programmed ventricular stimulation in patients with sustained monomorphic ventricular tachycardia.

OBJECTIVES: The aim of this study was to assess the ability of the signal-averaged electrocardiogram (ECG) to predict the efficacy of procainamide. BACKGROUND: The main role of the signal-averaged ECG has been the identification of postinfarction patients at risk of sudden death. Prediction of the efficacy of antiarrhythmic drugs represents another potential clinical application of this technique. METHODS: The study examined the effects of procainamide on the time domain and spectral temporal analysis of the signal-averaged ECG in relation to the results of programmed ventricular stimulation studies in 31 patients with inducible sustained monomorphic ventricular tachycardia. RESULTS: Procainamide significantly prolonged the total and the initial QRS complex and low amplitude signal durations (mean +/- SD 135 +/- 30 vs. 161 +/- 46 ms, p < 0.0001; 87 +/- 16 vs. 98 +/- 20 ms, p < 0.0001, and 48 +/- 23 vs. 63 +/- 36 ms, p < 0.001, respectively) whereas the root-mean-square voltage of the total QRS complex and of the last 40 ms of the QRS complex was significantly reduced (mean +/- SD 112 +/- 36 vs. 87 +/- 36 microV, p < 0.0001; 21 +/- 19 vs. 13 +/- 12 microV, p < 0.002, respectively). The results of spectral temporal mapping of the signal-averaged ECG were similar before and after procainamide administration. Procainamide prevented the inducibility of sustained ventricular tachycardia or prolonged the cycle length of ventricular tachycardia by > or = 100 ms in 16 patients (52%) (responders). The fractional prolongation of the total QRS duration was significantly greater in responders (26 +/- 15%) than in nonresponders (10 +/- 10%) (p < 0.002) and, when this prolongation was > or = 15%, identified responders with a sensitivity of 94%, a specificity of 87% and an overall predictive accuracy of 90%. CONCLUSIONS: The effects of procainamide on inducibility of ventricular tachycardia during programmed ventricular stimulation can be predicted by the degree of drug-induced prolongation of the signal-averaged QRS complex.

Aged↗
PubMed1993

The value of time and frequency domain, and spectral temporal mapping analysis of the signal-averaged electrocardiogram in identification of patients with hypertrophic cardiomyopathy at increased risk of sudden death.

Late potentials detected by the signal-averaged ECG (SAECG) identify post-infarction patients at risk from sustained ventricular tachycardia (VT) and sudden death. Hypertrophic cardiomyopathy (HCM) is also associated with increased risk of sudden death. In adults, episodes of non-sustained VT on ambulatory ECG monitoring are a marker of high risk patients. In children and adolescents, however, there is no reliable ECG marker, and clinical features have low predictive accuracy. The prognostic value of the SAECG in HCM has not been systematically evaluated. We examined the relation of detailed time domain, frequency domain, and spectral temporal mapping analysis of the SAECG and clinical and echocardiographic features, and the results of 48 h ambulatory ECG monitoring in 121 consecutive patients with HCM. Non-sustained VT on Holter monitoring was recorded in 27 (23%) patients. An abnormal time domain SAECG was present in three (11%) patients with VT vs three (3%) without VT (ns). Of the SAECG variables, reduced (below 150 microV) voltage of the initial 40 ms of the signal-averaged QRS complex was the best predictor for non-sustained VT (sensitivity: 95%; specificity: 74%: positive predictive accuracy: 64%; negative predictive accuracy: 97%). Nine patients (of whom eight were < or = 30 years of age) experienced catastrophic events: three died suddenly and six had been resuscitated from out-of-hospital ventricular fibrillation. None of them had an abnormal time domain SAECG. The frequency domain analysis and spectral temporal mapping of the SAECG did not improve the identification of patients with VT or patients with catastrophic events. In conclusion, alterations of the initial portion of the signal-averaged QRS complex identified patients with HCM and non-sustained VT, but the SAECG was not useful in identifying young patients who suffered cardiac arrest.

Action Potentials↗
PubMed1993

Frequency versus time domain analysis of the signal-averaged electrocardiogram: reproducibility of the spectral turbulence analysis.

Reproducibility of the Spectral Turbulence Analysis. Spectral turbulence analysis (STA) of the signal-averaged electrocardiogram (ECG) is a new frequency domain method that analyzes the total high gain QRS complex and not only its terminal portion. This study examined the qualitative and quantitative short-term reproducibility of this technique (three recordings made within 25 min) in 68 subjects: 16 healthy volunteers; 22 patients with ventricular tachycardia and no evidence of heart disease; and 30 postinfarction patients with sustained ventricular tachycardia. The reproducibility of diagnosis of the STA was compared with that of the conventional time domain analysis of the signal-averaged ECG using standard criteria of abnormality. The reproducibility of numeric values of the spectral turbulence and of the time domain indices was performed by computing the ratios between standard deviation of measurements in individual subjects and standard deviations of all measurements. The reproducibility of diagnostic conclusions of the time domain analysis was slightly better than that of the STA but the differences were not significant (88%-91% of consistent time domain results vs 84% of consistent STA results). The numeric reproducibility of three STA parameters was slightly but not significantly inferior to that of the time domain indices whereas the reproducibility of the fourth STA variable, the intersegment correlation standard deviation (ISCSD), was significantly worse than that of the other indices. Of the two different ECG segments analyzed, the reproducibility of the STA variables calculated for the total QRS region was significantly better than that of the terminal low power QRS region. In conclusion, the qualitative and quantitative reproducibility of the STA is slightly but not significantly worse than that of the time domain analysis with the exception of the ISCSD, which is significantly less reproducible than all other parameters.

Adult↗