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W Zareba

Publications and source records attributed to W Zareba.

At least 55 records · Page 3Linked to original sources
PubMed1998

TU wave area-derived measures of repolarization dispersion in the long QT syndrome.

The purpose of this study was to evaluate area-derived parameters of repolarization dispersion in LQTS patients and their unaffected family members and to use this analysis to challenge the concept of dispersion of repolarization in surface ECG. The area under the curve between the J point and the next P wave was measured automatically in 12 leads of the digital ECG in 34 LQTS patients and 22 unaffected family members. The area-derived measures of repolarization included total repolarization area, T wave amplitude, time to accumulate the first (tA50) and the median (tA25-75) 50% of the total area, and the time to accumulate 97% of the total repolarization area (tA97). In comparison with unaffected family members, LQTS patients had significantly higher dispersion of tA50 (tA50-SD = 34 +/- 18 ms vs 11 +/- 6 ms, respectively, P < .001) and tA25-75 (t[A25-75]-SD = 44 +/- 19 ms vs 24 +/- 15 ms, respectively, P < .001), whereas no significant difference was observed in the dispersion of total repolarization area, T wave amplitude, and time to accumulate total repolarization area (tA97-SD = 44 +/- 20 ms vs 53 +/- 19 ms, respectively, ns). It is concluded the analysis of area-derived parameters of repolarization showed that LQTS patients have increased interlead variability of the repolarization morphology (tA50-SD and t[A25-75]-SD), whereas they do not have increased dispersion of the total repolarization duration (tA97-SD). This observation indicates that an increase in traditional measures of dispersion (QT dispersion) may represent a heterogeneity of repolarization shape, whereas the true dispersion of the total duration of repolarization, which is related to electrocardiographic lead projection, is similar in patients and healthy subjects.

Electrocardiography↗
PubMed1998

ECG features of microvolt T-wave alternans in coronary artery disease and long QT syndrome patients.

UNLABELLED: T-wave alternans (TWA) is a marker of myocardial electrical instability. We compared ECG features of microvolt TWA in coronary artery disease (CAD) and long QT syndrome (LQTS) patients. METHOD: The study populations consisted of 43 CAD and 39 LQTS patients. TWA was detected in resting Holter recordings using the new correlation method (CM). After preprocessing to adjust for RR variability and respiratory modulation, CM was used to quantify TWA amplitude (A(CM)), duration (N(CM)), and magnitude (MAG(CM); defined as the product of A(CM) and N(CM)). RESULTS: TWA was detected in 19 (44%) CAD and 17 (44%) LQTS patients. TWA was associated with longer RR intervals (P = 0.006) and had larger magnitudes (P = 0.067) in LQTS than CAD patients. The TWA was identified as transient (nonstationary) in 15 of 19 (79%) TWA-positive CAD patients, and in 8 of 17 (47%) TWA-positive LQTS patients (P = 0.047). CONCLUSIONS: The frequency of TWA detected with CM is similar in LQTS and CAD patients. TWA is larger in LQTS than in CAD patients, whereas TWA is more frequently transient (nonstationary) in LAD than LQTS patients. In LQTS patients, but not in CAD patients, a longer RR is associated with TWA, indicating different electrophysiologic mechanisms in the two pathologies.

Adult↗
PubMed1997

Electrocardiographic findings in patients with diphenhydramine overdose.

QT interval prolongation and torsades de pointes ventricular tachycardia have been reported after therapeutic doses and overdosage of second generation antihistamines, such terfenadine and astemizol. Diphenhydramine (DPHM), a first generation H1 antagonist, is the most frequently used antihistaminic drug. Despite its widespread use, there are no data about cardiac action and electrocardiographic consequences of DPHM overdose. The 12-lead electrocardiograms of 126 patients (mean age 26 +/- 11 years) who had DPHM overdose were evaluated. The ingestion of large doses of DPHM (in majority of cases the dose was >500 mg) was primarily suicidal. Repolarization duration, dispersion, and morphology were evaluated in DPHM overdose patients and compared with those of healthy subjects. Mean heart rate of DPHM overdose patients was 103 +/- 25 beats/min. The QTc duration was significantly longer (453 +/- 43 vs 416 +/- 35 ms, respectively, p <0.001) and mean T-wave amplitude significantly lower (0.20 +/- 0.10 vs 0.33 +/- 0.15 mV, respectively, p <0.001) in DPHM-overdose patients than in control subjects. Dispersion of repolarization was significantly lower in DPHM-overdose patients than in control subjects (42 +/- 25 vs 52 +/- 21 ms, respectively; p = 0.003). None of the DPHM-overdose patients experienced torsades de pointes. In conclusion, DPHM overdose is associated with a significant increase in heart rate and a significant but moderate QTc prolongation. None of the studied patients, including those who had apparent QTc prolongation, experienced torsades de pointes ventricular tachycardia.

Adult↗
PubMed1997

Clinical implications of silent versus symptomatic exercise-induced myocardial ischemia in patients with stable coronary disease.

OBJECTIVES: This study was undertaken to better understand the functional and prognostic significance of silent relative to symptomatic ischemia. BACKGROUND: Previous studies have reached conflicting conclusions as to whether painless ischemia identified during noninvasive cardiac testing is related to a lesser extent of myocardial ischemia or a different prognosis than ischemia accompanied by angina, or both. METHODS: Nine hundred thirty-six clinically stable patients 1 to 6 months after an acute coronary event, either myocardial infarction or unstable angina, underwent ambulatory monitoring, exercise treadmill testing and stress thallium-201 scintigraphy. They were then followed up prospectively for a mean of 23 months for recurrent cardiac events (cardiac death, nonfatal myocardial infarction or unstable angina). RESULTS: Compared with patients with symptomatic ischemia during testing (n = 125), those with silent ischemia (n = 378) demonstrated less severe and extensive reversible defects on stress thallium scintigraphy (p = 0.0008), less functional impairment during treadmill testing manifested by longer exercise duration (640 +/- 173 vs. 529 +/- 190 s, p = 0.002) and longer time to ST segment depression (530 +/- 215 vs. 419 +/- 205 s, p = 0.0001) and less frequent ST segment depression during ambulatory monitoring (9% vs. 19%, p = 0.005). Patients with symptomatic ischemia had a significantly (p = 0.004) increased number of subsequent recurrent cardiac events (28.8%) versus those with silent (18.0%) or no (17.3%) ischemia. Adverse outcomes were especially concentrated in the subgroup with symptomatic ischemia and poor exercise tolerance. The difference in cardiac event rates between patients with silent versus symptomatic ischemia persisted after adjustment for baseline clinical characteristics by Cox regression analysis. CONCLUSIONS: Patients with painless ischemia during exercise testing 1 to 6 months after recovery from a coronary event have less jeopardized ischemic myocardium and fewer recurrent cardiac events than patients with symptomatic ischemia.

Adult↗
PubMed1997

Prognostic value of cholesterol in women of different ages.

We assessed the short-term and long-term prognostic relationship between cholesterol and mortality in women of different ages with the aid of statistical graphics. Our population-based cohort study involved 2873 women in the Framingham Heart Study, with a median follow-up of 31 years. The primary outcome was all-cause mortality. Secondary outcome measures were coronary heart disease, noncoronary heart disease, and stroke mortality. We found that significant age interactions were present in the relationships between total cholesterol and mortality from all causes, coronary heart disease (CHD), stroke, and non-CHD causes. For women ages < or = 55, cholesterol is related positively to both short-term (p > 0.05) and long-term (p = 0.05) all-cause mortality. For women ages 56-70, there are significant U-shaped relationships between cholesterol and both short-term and long-term all-cause mortality (p < 0.01). Lowest short-term and long-term mortality rates for women in this age group are at cholesterol values between 240 and 280 mg/dl. For women ages > 70, cholesterol < 240 mg/dl is associated with increased short-term mortality (p < 0.01), and no significant long-term association was detected. These cholesterol/mortality relationships and age interactions can be explained by patterns of association between mortality and both high- and low-density lipoprotein cholesterol among women in the different age groups. These results do not support the hypothesis that cholesterol < 200 mg/dl leads to decreased mortality in women > 55 years old.

Adult↗
PubMed1995

ECG T-wave patterns in genetically distinct forms of the hereditary long QT syndrome.

BACKGROUND: The long QT syndrome is an inherited disorder with prolonged ventricular repolarization and a propensity to ventricular tachyarrhythmias and sudden arrhythmic death. Recent linkage studies have demonstrated three separate loci for this disorder on chromosomes 3, 7, and 11, and specific mutated genes for long QT syndrome have been identified on two of these chromosomes. We investigated ECG T-wave patterns (phenotypes) in members of families linked to three genetically distinct forms of the long QT syndrome. METHODS AND RESULTS: Five quantitative ECG repolarization parameters, ie, four Bazett-corrected time intervals (QTonset-c, QTpeak-c, QTc, and Tduration-c, in milliseconds) and the absolute height of the T wave (Tamplitude, in millivolts), were measured in 153 members of six families with long QT syndrome linked to markers on chromosomes 3 (n = 47), 7 (n = 30), and 11 (n = 76). Genotypic data were used to define each family member as being affected or unaffected with long QT syndrome. Affected members of all six families had longer QT intervals (QTonset-c, QTpeak-c, or QTc) than unaffected family members (P < .01). Each of the three long QT syndrome genotypes was associated with somewhat distinctive ECG repolarization features. Among affected individuals, the QTonset-c was unusually prolonged in those individuals with mutations involving the cardiac sodium channel gene SCN5A on chromosome 3 (lead II QTonset-c [mean +/- SD]: chromosome 3, 341 +/- 42 ms; chromosome 7, 290 +/- 56 ms; chromosome 11, 243 +/- 73 ms; P < .001); Tamplitude was generally quite small in the chromosome 7 genotype (lead II Tamplitude, mV: chromosome 3, 0.36 +/- 0.14; chromosome 7, 0.13 +/- 0.07; chromosome 11, 0.37 +/- 0.17; P < .001); and Tduration was particularly long in the chromosome 11 genotype (lead II Tduration-c: chromosome 3, 187 +/- 33 ms; chromosome 7, 191 +/- 51 ms; chromosome 11, 262 +/- 65 ms; P < .001). Similar ECG findings were observed in leads aVF and V5. A considerable variability exists in the quantitative repolarization parameters associated with each genotype, with overlap in the T-wave patterns among the three genotypes. CONCLUSIONS: Three separate genetic loci for the long QT syndrome including mutations in two cardiac ionic channel genes were associated with different phenotypic T-wave patterns on the ECG. This study provides insight into the influence of genetic factors on ECG manifestations of ventricular repolarization.

Adult↗
PubMed1995

Risk of cardiac events in family members of patients with long QT syndrome.

OBJECTIVES: This study sought to identify risk factors for cardiac events (syncope, aborted cardiac arrest or sudden cardiac death) in family members of patients with the long QT syndrome. BACKGROUND: Patients with the long QT syndrome are known to be at high risk for cardiac events. Whenever the first member of a family is identified as having the long QT syndrome (proband), there is concern regarding the likelihood of cardiac events in other family members. METHODS: A multivariate logistic regression model was used to evaluate the risk of cardiac events in 637 family members who were first- and second-degree relatives of 151 probands with the long QT syndrome and in a subset of 513 family members who were not receiving beta-adrenergic blocking agents. There were 293 first-degree (46%) and 344 second-degree relatives (54%) (293 men [46%], 344 women [54%]). Fifteen percent of the family members had a corrected QT interval (QTc) > 0.44 s, and relative tachycardia and bradycardia were observed in 12% and 25%, respectively. RESULTS: The risk of cardiac events occurring before age 40 in family members not taking beta-blockers was influenced by the QTc interval (odds ratio [OR] 1.18/0.01 increase in QTc value; 95% confidence interval [CI] 1.12 to 1.24), relative tachycardia (OR 2.21, 95% CI 0.97 to 5.02) or bradycardia (OR 2.24, 95% CI 1.10 to 4.56) and an interaction term combining gender and closeness of the relationship to the proband (OR for female first-degree relative 3.23 vs. all second-degree relatives, 95% CI 1.67-6.22). CONCLUSIONS: Female first-degree relatives of patients with the long QT syndrome have a higher risk of cardiac events than male first- or second-degree relatives, independent of recorded electrocardiographic findings. Not only bradycardia, but also tachycardia increases risk of cardiac events in family members of patients with the long QT syndrome.

Adolescent↗
PubMed1995

Dispersion of repolarization. Relation to heart rate and repolarization duration.

Repolarization duration is highly dependent on heart rate. A major concern when evaluating dispersion of repolarization is the possible influence of heart rate on the magnitude of dispersion. Another consideration relates to a potential relationship between overall duration of repolarization and the magnitude of dispersion, that is, whether patients with longer repolarization duration present with increased or decreased dispersion of repolarization. Therefore, the following relationships were studied in 380 normal subjects, 68 coronary artery disease (CAD) patients, and 41 long QT syndrome (LQTS) patients: the magnitude of dispersion (JTd) versus cycle length (R-R) and dispersion versus repolarization duration (QTc interval). Dispersion of repolarization (JTd), measured as the maximal difference in JT interval duration between precordial leads, was significantly higher in LQTS patients than in normal subjects or CAD patients (120 +/- 72 vs 53 +/- 42 and 48 +/- 22 ms, respectively). In neither normal subjects, CAD patients, or LQTS patients were there significant relationships between the magnitude of dispersion and the R-R interval (r = .094, .158, and .233, respectively; not significant) and between the magnitude of dispersion and QTc duration (r = .0443, -.094, and .126, respectively; not significant). In normal subjects, CAD patients, and LQTS patients, the magnitude of dispersion is not significantly related to heart rate, indicating that there is no need for heart rate adjustment of dispersion parameters. In addition, there is no significant association between the magnitude of dispersion and duration of repolarization.

Adult↗
PubMed1994

Dispersion of ventricular repolarization and arrhythmic cardiac death in coronary artery disease.

In a recent prospective study of myocardial ischemia, arrhythmic cardiac death occurred in 17 of 936 patients (2%) during a 2-year follow-up after acute myocardial infarction or unstable angina. Dispersion of ventricular repolarization was evaluated on the 12-lead electrocardiogram at enrollment in 17 patients who subsequently died of cardiac arrhythmia and in 51 matched survivors. The aim of this study was to evaluate the relation between various measurements of dispersion of repolarization and subsequent arrhythmic cardiac death, and to determine if dispersion of repolarization makes an independent contribution to the risk of arrhythmic cardiac death. Ventricular depolarization quantitated in terms of mean QRS (QRS-m) duration, and ventricular repolarization quantitated in terms of mean (m), maximal-minimal dispersion (d), standard deviation (s), and coefficient of variation (cv) of QT and JT intervals, were determined. Univariate analyses revealed that 2 standard electrocardiographic parameters, QRS-m and QT-m, and 3 dispersion variables, JT-d, JT-s, and JTc-d, were associated with arrhythmic cardiac death (p < 0.01). Multivariate analyses revealed that the combination of the dispersion parameter (JT-d, JT-s, or JTc-d) and QRS-m made an independent contribution to the risk of arrhythmic cardiac death. The findings highlight the importance of both delayed depolarization and heterogenous repolarization as risk factors for arrhythmic cardiac death. Thus, increased dispersion of repolarization is associated with an elevated likelihood of arrhythmic cardiac death. Prolonged QRS duration and increased dispersion of repolarization make independent contributions to the risk of arrhythmic cardiac death in patients with coronary artery disease.

Aged↗
PubMed1994

T wave alternans in idiopathic long QT syndrome.

OBJECTIVES: The study evaluates the association between T wave alternans and the risk of cardiac events (syncope, aborted cardiac arrest or cardiac death) in a large population of patients with idiopathic long QT syndrome. BACKGROUND: T wave alternans is an infrequently recorded electrocardiographic (ECG) finding in patients with delayed repolarization, and its clinical significance is not clear. METHODS: A total of 4,656 ECG recordings in 2,442 patients enrolled in the International Long QT Syndrome Registry were reviewed for episodes of T wave alternans. To determine the risk associated with T wave alternans, independent of corrected QT interval (QTc) duration, patients with T wave alternans were matched for QTc value (every 0.025 s1/2) to patients with long QT syndrome without T wave alternans. RESULTS: T wave alternans was identified in 30 patients (25 of whom had a QTc interval > 0.50 s1/2). A strong association between QTc prolongation and T wave alternans was observed (odds ratio 1.23 per 0.01-s1/2 unit increase in QTc, p < 0.0001). Conditional logistic regression analyses with adjustment for age, gender, status and QTc value revealed that T wave alternans did not make a significant independent contribution to the risk of cardiac events. The risk of experiencing a major cardiac event was primarily related to length of QTc. CONCLUSIONS: T wave alternans, a marker of electrical instability and regional heterogeneity of repolarization, identifies a high risk subset of patients with prolonged repolarization. Patients with T wave alternans have an increased risk of cardiac events, but this risk is primarily related to the magnitude of repolarization delay (QTc prolongation). T wave alternans does not make an independent contribution to the risk of cardiac events after adjustment for QTc length.

Adolescent↗
PubMed1994

Automatic detection of spatial and dynamic heterogeneity of repolarization.

Heterogeneity of ventricular repolarization is associated with the development of life-threatening ventricular arrhythmias. Temporal heterogeneity of repolarization may be manifest in an individual beat (spatial heterogeneity) or in a sequence of beats (dynamic heterogeneity). Spatial inhomogeneity of repolarization throughout the myocardium may be expressed electrocardiographically as dispersion of repolarization durations computed in simultaneously recorded leads. The beat-to-beat changes in the repolarization pattern (duration and/or amplitude) may account for a dynamic (time-dependent) dimension of heterogeneity, occasionally seen as T-wave alternans. A visual detection of heterogeneous repolarization is a time-consuming, observer-dependent, and frequently inaccurate process. Therefore, we developed computer algorithms designed to detect automatically (1) dispersion of repolarization and (2) nonvisible T-wave alternans from digitally recorded (1,000 Hz) X, Y, and Z electrocardiogram leads. This automatic approach was subsequently tested in 10 patients with idiopathic long QT syndrome and in 10 age-matched normal subjects. Long QT syndrome patients presented with significantly higher indices of heterogeneity in comparison with the control subjects; the dispersion of repolarization was 44 +/- 11 and 13 +/- 6 ms, respectively (P < .01), and T-wave alternans index was 0.40 +/- 0.37 and 0.03 +/- 0.06, respectively (P < .01). Simultaneous evaluation of spatial (dispersion of repolarization) and dynamic (T-wave alternans) aspects of repolarization provides new insight into heterogeneity of electrical recovery after myocardial depolarization. The automatic detection of repolarization dispersion and T-wave alternans in digital electrocardiogram recordings provides a practical method to evaluate heterogeneity of repolarization and may be useful for stratifying patients at risk of ventricular arrhythmias.

Arrhythmias, Cardiac↗
PubMed1994

Risk of subsequent cardiac events in stable convalescing patients after first non-Q-wave and Q-wave myocardial infarction: the limited role of non-invasive testing. The Multicenter Myocardial Ischemia Research Group.

BACKGROUND: Patients recovering from myocardial infarction are frequently evaluated by non-invasive tests for evidence of myocardial ischemia before returning to work or full activity. The purpose of this study was to evaluate the prognostic significance of clinical and non-invasive ischemic test variables assessed in 549 stable, convalescing patients (median 2 months) after their first Q-wave (n = 363) and non-Q-wave (n = 186) myocardial infarction. METHODS: The ischemic tests performed were resting ECG, exercise ECG, ambulatory ECG, and stress thallium scintigraphy. RESULTS: Cardiac events (unstable angina requiring hospitalization, non-fatal reinfarction, or death from cardiac causes) were observed during a mean 23-month follow-up in 57 patients (15.7%) with Q-wave and in 31 of patients (16.7%) with non-Q-wave infarction. In a step-wise Cox regression model, the only significant independent predictors of subsequent cardiac events (P < 0.001) were post-infarction angina and insulin-dependent diabetes mellitus. The type of infarction did not make a significant contribution to the risk of cardiac events (P = 0.29). However, an interaction between infarct type and post-infarction angina was of borderline significance (P = 0.065), with angina associated with more cardiac events in patients with non-Q-wave than in those with Q-wave infarction. None of the ischemic tests contributed significantly to the Cox model in predicting cardiac events in either infarct type. CONCLUSION: Stable convalescing patients who have recovered from first Q-wave and non-Q-wave myocardial infarction have similar long-term prognoses. The occurrence of post-infarction angina is associated with increased risk of cardiac events in patients with both infarct types, with more marked effect in non-Q-wave than Q-wave infarctions. Ischemia detected by non-invasive tests performed in the convalescing phase after myocardial infarction was not prognostically useful in either infarct type.

Convalescence↗
PubMed1994

Risk of subsequent cardiac events in stable convalescing patients after first non-Q-wave and Q-wave myocardial infarction: the limited role of non-invasive testing.

BACKGROUND: Patients recovering from myocardial infarction are frequently evaluated by non-invasive tests for evidence of myocardial ischemia before returning to work or full activity. The purpose of this study was to evaluate the prognostic significance of clinical and non-invasive ischemic test variables assessed in 549 stable, convalescing patients (median 2 months) after their first Q-wave (n = 363) and non-Q-wave (n = 186) myocardial infarction. METHODS: The ischemic tests performed were resting ECG, exercise ECG, ambulatory ECG, and stress thallium scintigraphy. RESULTS: Cardiac events (unstable angina requiring hospitalization, non-fatal reinfarction, or death from cardiac causes) were observed during a mean 23-month follow-up in 57 patients (15.7%) with Q-wave and in 31 of patients (16.7%) with non-Q-wave infarction. In a step-wise Cox regression model, the only significant independent predictors of subsequent cardiac events (P < 0.001) were post-infarction angina and insulin-dependent diabetes mellitus. The type of infarction did not make a significant contribution to the risk of cardiac events (P = 0.29). However, an interaction between infarct type and post-infarction angina was of borderline significance (P = 0.065), with angina associated with more cardiac events in patients with non-Q-wave than in those with Q-wave infarction. None of the ischemic tests contributed significantly to the Cox model in predicting cardiac events in either infarct type. CONCLUSION: Stable convalescing patients who have recovered from first Q-wave and non-Q-wave myocardial infarction have similar long-term prognoses. The occurrence of post-infarction angina is associated with increased risk of cardiac events in patients with both infarct types, with more marked effect in non-Q-wave than Q-wave infarctions. Ischemia detected by non-invasive tests performed in the convalescing phase after myocardial infarction was not prognostically useful in either infarct type.

Angina Pectoris↗