Biomedical subjects
Publications and source records attributed to M Malik.
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Tumoral calcinosis is an uncommon condition which usually appears in the region of large joints. It is rare in the hand. We present two cases affecting the fingers. No causative abnormality was found.
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Depressed baroreceptor sensitivity (BRS) has been associated with an increased risk of ventricular arrhythmias and sudden cardiac death after myocardial infarction, but the influence of thrombolytic therapy on BRS has not been examined. To determine the effect of thrombolytic therapy on the evolution of BRS after myocardial infarction, BRS was assessed at 6 days, 6 weeks, and 3 months in 76 patients, 53 (70%) of whom had received thrombolytic therapy. The mean age (57 vs 57 years), sites of infarction, and the proportion of patients taking beta-blockers (68% vs 52%) did not differ between patients who did and those who did not receive thrombolytic therapy. There was no difference in predischarge mean left ventricular ejection fractions (42% vs 46%) between the two groups of patients, but mean baseline BRS was 9.2 (0.8) msec/mm Hg in patients who were treated with thrombolysis and 5.9 (1.3) msec/mm Hg in those who were not (p = 0.03). At 6 weeks the corresponding values were 9.7 (1.1) and 11.1 (2.8) msec/mm Hg (p = 0.6) and at 3 months 9.1 (1.0) and 6.5 (1.1) msec/mm Hg (p = 0.07). At baseline 13% of patients who were treated with thrombolysis and 13% of those who were not had BRS < 3.0 msec/mm Hg, but at 3 months 9% of patients who were treated with thrombolytic agents compared with 17% of those who had BRS < 3.0 msec/mm Hg. In conclusion, early after myocardial infarction mean BRS was higher in patients treated with thrombolysis compared with nontreated patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Occlusion of the infarct-related artery has recently been associated with an increased risk of sudden death, particularly in patients with poor left ventricular function. Depressed heart rate variability (HRV) also identifies postinfarction patients at an increased risk of sudden death. The correlation between infarct artery patency, left ventricular function, and HRV was therefore examined in 186 survivors of a first myocardial infarction. Predischarge coronary angiography and Holter monitoring were carried out in 186 patients with a first acute myocardial infarction. Coronary angiography was performed because of abnormal predischarge exercise test findings. Mean age (56 +/- 9 years) and the proportions of type and site of infarction did not differ between patients with occluded or patent arteries or between patients who did or did not undergo coronary angiography. The mean left ventricular ejection fraction (EF) was 55 +/- 15% in patients with patent and 49 +/- 14% in those with occluded infarct arteries (p < 0.001), and the EF was < 40% in 17% and 28% of the respective groups (p < 0.05). HRV was < 20 U in 7 (18%) of the 39 patients with an EF < 40% but in only 7 (5%) of the 147 patients with an EF > 40% (p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
Spectral methods for the assessment of heart rate variability (HRV) in 24-h electrocardiograms (ECG) are believed to require visual verification and manual editing of the computerised recognition of the ECG. This study investigated the effect of the recognition errors of computerised ECG recognition on two methods providing spectral HRV indices: (a) Fast Fourier Transformation (FFT); and (b) peak-to-trough analysis (PTA). Both methods were used to measure HRV spectra in 24-h ECGs recorded in 557 survivors of acute myocardial infarction. Each ECG was analysed using the Marquette 8000 Holter system and spectral HRV analyses were performed both prior to and after manual verification of the automatic ECG analysis. The FFT and PTA methods were used to calculate the low (0.04-0.15 Hz), medium (0.15-0.40 Hz) and high (0.40-1.00 Hz) HRV spectral components. For each method and for each spectral component, the rank correlations between the results obtained from unedited and edited ECG recognition were calculated. The correlations between the corresponding spectral components provided by the FFT and PTA methods applied to the edited recognitions were also calculated. Both methods were substantially affected by recognition errors. The FFT method was more sensitive to the misrecognition than the PTA method. The inter-method correlations were higher for the high and medium spectral components than for the low spectral component. The study suggests that spectral HRV analysis should be performed only on carefully verified and manually corrected recognitions of long-term electrocardiograms.
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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.
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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.
This study compared short-term (1 day) and long-term (1 week and 1 month) reproducibility of the numerical results of 21 individual indices of time-domain analysis, spectral temporal mapping, and spectral turbulence analysis of the signal-averaged electrocardiogram in 28 healthy volunteers (18 men, 10 women, mean age, 31 years; range, 22-39 years). For each of the 21 indices and for each of the repeated recordings (ie, recordings on day 1, 7, and 30), the mean relative error versus recording of day 0 was calculated together with the rank correlation coefficient. The study showed that (1) reproducibility of time-domain analysis with the 40-Hz high-pass filter was superior to that of time-domain analysis performed with the 25-Hz high-pass filter, (2) reproducibility of time-domain variables was similar to that of spectral turbulence analysis of the entire QRS complex and was superior to that of spectral temporal mapping, (3) reproducibility of frequency-domain techniques not based on time-domain measurements (such as spectral turbulence analysis of the entire QRS complex) was significantly better than that of frequency-domain techniques combined with time-domain measurements (such as spectral turbulence analysis of the low-power terminal QRS region or spectral temporal mapping), and (4) short- and long-term reproducibility of signal-averaged electrocardiographic indices is similar in a healthy population.
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Numerous studies have reported a correlation between production of 72-kDa (MMP-2) and 92-kDa (MMP-9) type-IV collagenases/gelatinases and the metastatic potential of cancer cells. An abrogating effect of tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) on metastases has also been noted. In this report we have used sensitive enzyme-linked immunoassays to measure MMP-2, MMP-9, TIMP-1 and TIMP-2 levels in eight human lung-cancer cell lines which were characterized for biological behavior in nude mice. We demonstrated that the Calu-6 and A549 cell lines with the highest metastatic, invasive and tumorigenic potential secreted the highest levels of MMP-2. MMP-9 and TIMP-1 secretions were comparatively low in all cell lines. TIMP-2 secretion, which exceeded MMP-2 secretion for all cell lines, did not correlate with metastatic potential. To further explore these correlations, the metastatic Calu-6 cell line was transfected with a K-rev-1 cDNA expression construct. The K-rev revertant cell lines demonstrated a more differentiated phenotype and were less tumorigenic, invasive and metastatic in nude mice. Nonetheless, the Calu-6 revertant cell lines secreted higher levels of MMP-2 than the parent cell line. In conclusion, invasion and metastasis by lung-cancer cells requires not only enhanced MMP production, but also other less well-understood tumorigenic characteristics. The multiplicity of factors required by cancer cells for dissemination helps to explain the minute fraction of cancer cells from a primary tumor that ever develop into a metastasis.
Standard time domain variables from signal-averaged electrocardiography were examined in a population of 331 survivors of acute myocardial infarction. Of these subjects, 130 received early (less than 24 hours) thrombolytic therapy. During a follow-up of greater than or equal to 10 months, there were 17 arrhythmic events (8.5%) (sudden death or sustained symptomatic ventricular tachycardia) in the group without thrombolysis and 8 (6.2%) in those with thrombolysis. Statistically, highly significant differences between the signal-averaged electrocardiographic variables of patients with and without arrhythmic events were found in the group without thrombolysis, whereas only root-mean-square voltage of the terminal 40 ms of the signal-averaged QRS complex was statistically associated with outcome (the differences in the other 2 indexes being not significant) in patients with thrombolysis. When using 2 previously published categoric criteria for the diagnosis of abnormal signal-averaged electrocardiography, the performance of these criteria in predicting arrhythmic events was substantially better in the group without thrombolysis than in those with thrombolysis (positive predictive accuracy greater than 3 times lower). Retrospectively adjusted receiver-operator characteristics showed that for a sensitivity of 30%, the maximum achievable positive predictive accuracy of signal-averaged electrocardiography for arrhythmic events was 100% in the group without thrombolysis, but only 27% in those with thrombolysis. It is concluded that standard signal-averaged electrocardiography after acute myocardial infarction is less informative in patients who receive thrombolytic treatment.