Junctional rhythm quantity and duration during slow pathway radiofrequency ablation in patients with atrioventricular nodal re-entry supraventricular tachycardia.

AIM: The occurrence of accelerated junctional rhythm during radiofrequency energy delivery at the region of the slow pathway is a well-recognized marker of successful treatment of atrioventricular nodal re-entry tachycardia (AVNRT). Our aim was to evaluate if the quantity and duration of accelerated junctional rhythm during radiofrequency ablation of the slow pathway is correlated with residual slow pathway conduction. METHODS AND RESULTS: Forty consecutive patients with AVNRT undergoing radiofrequency ablation of slow pathway who developed accelerated junctional rhythm during ablation were included. We compared accelerated junctional rhythm quantity and duration between two groups: group A, without echo beats and group B, with echo beats on post-ablation electrophysiology study. The total amount of accelerated junctional rhythm was significantly greater in group A than in group B [75.0 (63.5-165.0) vs. 36.0 (24.0-65.0), P=0.006], as well as total duration of accelerated junctional rhythm [47.0(33.5-81.0) s vs. 23.0 (16.0-42.0) s, P=0.006]. The cycle length of accelerated junctional rhythm did not differ between the two groups [510.0 (445.0-545.0) ms vs. 500.0 (450.0-585.0) ms, P=0.5). CONCLUSIONS: The amount and duration of accelerated junctional rhythm is correlated with the total abolishment abolition of slow pathway conduction. A higher amount and duration of accelerated junctional rhythm during radiofrequency applications may be an additional marker of successful ablation.

Are neutrons involved in the pathogenesis of life-threatening cardiac arrhythmias?

Geomagnetic fields protect the earth from the adverse effects of cosmic rays, whose activity can be indirectly measured by monitoring the level of neutrons in the environment. The number and days of discharges from automatic implantable cardioverter defibrillators (ICD) in patients with cardiac arrhythmias are inversely correlated with the daily level of geomagnetic activity (GMA). The aim of the present was to determine whether neutron levels on days of AICD discharges are higher than average. Days on which discharges occurred were recorded in 31 patients bearing ICDs for managing ischemic cardiomyopathy. Daily neutron levels obtained from the monitoring data of the Russian Academy of Sciences in Moscow were analyzed using Student's t test. The mean (+/-SD) daily neutron level for the 1096-day period was 8299.29 +/- 294.236 imp/min (median 8252), and for days of ACID discharge, 8423.93 +/- 274.187 imp/min (median 8443) (p = 0.0002). The mean neutron activity on days of AICD discharges in response to ventricular disturbances was significantly higher than the mean level over the 1096-day study period. Whether this relation is a direct result of low GMA or due to an independent role of neutrons in the pathogenesis and timing of cardiac arrhythmias is unknown.

Heart rate variability in elderly patients before and after electroconvulsive therapy.

Earlier studies have found major depression to be associated with increased cardiac mortality, hypothesized to result from reduced vagal modulation. Since reduced heart rate variability is part of normal aging, depression might predispose elderly patients to a higher risk. The authors investigated cardiac autonomic modulation, using spectral analysis, in 11 elderly depressed inpatients before and after electroconvulsive therapy (ECT). Cardiac vagal modulation increased significantly after ECT and was associated with symptom improvement, assessed by a significant decrease in the Hamilton Rating Scale for Depression. Further research is needed to elucidate the relationship between depression, autonomic modulation, and clinical risks in elderly patients.

Insulin resistance is increased by transdermal estrogen therapy in postmenopausal women with cardiac syndrome X.

Estrogen has been reported to have both short- and long-term effects on the cardiovascular system. However, it remains to be examined how short-term transdermal estrogen therapy (TET) affects insulin sensitivity (SI) in patients with cardiac syndrome X (CSX), who are characterized by elevated insulin resistance. SI was assessed in a randomized, double-blind, placebo-controlled crossover study by minimal model analysis in seven postmenopausal women with CSX treated by TET. SI decreased by 32 +/- 8.3%, from 5.94 +/- 1.14 at baseline to 3.61 +/- 0.40 [(10(-4) x min(-1))/(microU/ml)] during TET (p = 0.03). Time to the onset of symptoms increased from 414.2 +/- 51.0 s at baseline to 450.0 +/- 53.2 s (p = 0.04). We conclude that TET increases SI in postmenopausal women with CSX. This effect is unrelated to the beneficial anti-ischemic effects on exercise duration.

Prediction of the extent and severity of left ventricular dysfunction in anterior acute myocardial infarction by the admission electrocardiogram.

BACKGROUND: The grade of ischemia, as detected by the relation between the QRS complex and ST segment on the admission electrocardiogram, is associated with larger infarct size and increased mortality rates in acute myocardial infarction. METHODS: We assessed the correlation between left ventricular function and the admission electrocardiogram in 151 patients with first anterior acute myocardial infarction who received thrombolytic therapy and underwent cardiac catheterization at 90 minutes and before hospital discharge. The number of leads with ST elevation, sum of ST elevation, maximal Selvester score, and the presence of severe (grade 3) ischemia were determined in each electrocardiogram. Left ventricular ejection fraction, the number of chords with wall motion abnormalities, and the severity of dysfunction (SD/chord) were determined. RESULTS: At 90 minutes, the 39 ischemia grade 3 patients had lower ejection fraction than the 112 grade 2 patients. Both at 90 minutes and at hospital discharge, the grade 3 group had more chords with wall motion abnormalities and more severe regional dysfunction (SD/chord). However, the number of leads with ST elevation, sum of ST elevation, and maximal Selvester score had no correlation with ejection fraction at 90 minutes and only mild correlation with the extent of dysfunction (number of chords) at 90 minutes. There was no correlation between either the number of leads with ST elevation or the sum of ST elevation and the severity of regional dysfunction. CONCLUSIONS: The number of leads with ST elevation, sum of ST elevation, and maximal Selvester score had only mild correlation with the extent of myocardial dysfunction but not with the severity of dysfunction. Grade 3 ischemia is predictive of more extensive myocardial involvement and greater severity of regional dysfunction.

Impact of atrial fibrillation on clinical status, atrial size and hemodynamics in patients after mitral valve replacement.

BACKGROUND AND AIM OF THE STUDY: The association between mitral valve disease and atrial fibrillation (AF) is well known, but few data exist regarding the impact of AF after mitral valve replacement (MVR) on NYHA functional class, atrial size and hemodynamic parameters. The present study was conducted to evaluate these issues. METHODS: Eighty-six patients (26 men, 60 women) who underwent MVR were evaluated by transthoracic echocardiography. Fifty-nine patients had chronic AF (AF group), and 27 were in sinus rhythm (sinus group). Variables analyzed included end-systolic left atrial and right atrial areas, tricuspid regurgitation, and presence and duration of AF. Peak and mean transprosthetic mitral valve gradients and pulmonary pressure were estimated by Doppler echocardiography. RESULTS: Groups were matched for age, sex and time from MVR (mean 6.6 years). Sixty-four patients (77%) had rheumatic heart disease, 18 (21%) had mitral valve disease, and two (2%) had mitral valve prolapse. Mean duration of AF was 11+/-12 years (range: 8-50 years). Preoperatively, AF patients had a worse NYHA class than sinus patients (2.8+/-0.8 versus 1.1+/-0.7, p = 0.001), but both had similar fractional shortening of the left ventricle and preserved prosthetic mitral valve function. Multivariate analysis identified AF as a single predictor of NYHA class after MVR. Although left and right atrial areas were larger in AF patients (47+/-25 versus 27+/-7 cm2, p = 0.0001 and 30+/-12 versus 17+/-5 cm2, p = 0.0001, respectively), the left:right atrial size ratio was not significantly different between groups. Multivariate analysis identified mean transmitral gradient and duration of AF as independent predictors of left atrial size after MVR (p = 0.01 and p = 0.0001, respectively). Tricuspid regurgitation and duration of AF were independent predictors of right atrial size (p = 0.003 and p = 0.0001, respectively). CONCLUSION: The presence of AF after MVR is associated with a worse NYHA functional class, increased transmitral gradients, and larger areas of both atria, when compared with sinus rhythm. Hence, a special effort should be made to correct arrhythmia during surgery, and in case of paroxysmal arrhythmia, earlier surgery should be considered before the condition becomes chronic.

QT dispersion in the surface electrocardiogram in elderly patients with major depression.

BACKGROUND: QT dispersion (QTd) is a measure of interlead variations of QT interval of the surface 12-lead electrocardiogram (ECG). Increased QTd, found in various cardiac diseases, reflects cardiac instability and is associated with increased cardiac death. Major depressive disorder (MDD) was found to be associated with high cardiovascular mortality rates. This study compares QTd in elderly patients with MDD to normal controls. METHODS: QTd and rate-corrected QTd of 18 physically healthy elderly patients (69.9 +/- 7.6 years) with MDD was compared to nine physically and mentally healthy age- and gender-matched controls (64.1 +/- 12.2 years). RESULTS: QTd and rate-corrected QTd were significantly higher in MDD compared to controls (68 +/- 30 vs. 40 +/- 13 ms, P=0.002 and 81 +/- 39 vs. 43 +/- 13 ms, P=0.001, respectively). Intra- and inter- observer reproducibilities were highly correlated (r=0.96, P <0.0001; r=0.88, P <0.001, respectively). LIMITATIONS AND CONCLUSIONS: The major limitations of this study are the small number of subjects and the fact that all the patients were maintained on antidepressant medication. However, it seems that QTd analysis might shed light on possible autonomic imbalance and also provide a novel cardiovascular risk factor for increased cardiac death in MDD.

Correlation of predischarge electrocardiographic patterns with left ventricular function in patients with anterior wall myocardial infarction.

The aim of this prospective study was to assess the correlation between different predischarge electrocardiographic patterns and left ventricular function, evaluated by physical examination and echocardiography, in patients with first Q wave anterior acute myocardial infarction. A positive correlation was found between the electrocardiographic pattern and wall motion score assessed by echocardiography, reflecting a gradual worsening in left ventricular function among the different patterns. Patients with an isoelectric ST segment and negative T waves had a 73% decrease in the risk of clinical heart failure compared to those who continued to have ST elevation. Thus, a predischarge electrocardiogram can be used as a simple, noninvasive method for the risk stratification of patients with acute myocardial infarction.

Correlation between electrocardiographic subtypes of anterior myocardial infarction and regional abnormalities of wall motion.

BACKGROUND: Examination of the electrocardiogram is the most widely used means for diagnosis and early stratification of risk of acute myocardial infarction (AMI). The classical classification of the subtypes of anterior AMI is based on results of studies comparing the electrocardiograms recorded at various stages, mostly in the subacute or chronic stage of AMI, with autopsy findings. Reports regarding the correlation between electrocardiographic findings in the acute phase and regional abnormality of wall motion (AWM) detected by echocardiographic evaluation are sparse. OBJECTIVE: To investigate the relationship between the electrocardiographic and two-dimensional echocardiographic findings regarding patients with their first anterior AMI. DESIGN AND METHODS: We studied 58 patients, 44 men and 14 women of mean age 61.5 +/- 14.6 years, with their first anterior AMI who had undergone two-dimensional echocardiographic evaluation within 48 h of admission. Deviation of ST-segment trace from baseline was measured manually 0.06 s after the J point for all leads on the admission electrocardiogram. ST-segment elevation in the various leads was correlated to the incidence of regional AWM detected by echocardiography. RESULTS: ST-segment elevations > or = 0.1 mV in V1 leads were found for 21 (36.2%) patients. Basal anterior, basal anteroseptal, and basal septal AWM were seen more often for patients with than they were for patients without ST-segment elevation in V1 (57 versus 16%, P=0.003; 43 versus 13.5%, P=0.03; 43 versus 11%, P=0.01 respectively). In contrast to ST-segment elevation in lead V1, the only statistically significant difference in prevalence in the presence of regional AWM between patients with (n = 48) and without (n = 10) ST-segment elevation > or = 0.2 mV in lead V2 was in the inferoapical region (87.5 versus 40%; P=0.003). ST-segment elevation > or = 0.1 mV in leads aVL and V5 was found for 11 (19%) and 23 (40%) patients, respectively. There was no correlation between either lateral or apical regional AWM and the presence of ST-segment elevation in the anterolateral leads except for mid-lateral AWM, which was more often detected for patients with than it was for patients without ST-segment elevation in aVL leads (36.3 versus 6.4%, P=0.026). CONCLUSIONS: ST-segment elevation in lead V1 during the acute phase of anterior AMI is associated with a high incidence of regional AWM in the basal anterior, anteroseptal, and anterior regions, whereas ST-segment elevation in lead V2 is more often associated with AWM in the inferoapical region. ST-segment elevation in aVL leads is related to mid-lateral regional AWM.

Value of the initial electrocardiogram in patients with inferior-wall acute myocardial infarction for prediction of multivessel coronary artery disease.

BACKGROUND: Patients with inferior-wall acute myocardial infarction (AMI) who have ST-segment depression in the left precordial leads (LSTD+) on the initial electrocardiogram were reported to have more diffuse coronary artery disease (CAD) than had those without this finding (LSTD-). This suggests that LSTD+ patients may need extensive revascularization interventions more often than do LSTD- patients. However, this has not yet been confirmed. OBJECTIVE: To compare the coronary angiographic findings and treatment strategies for patients with inferior-wall AMI according to the LSTD pattern. METHODS: The clinical outcomes and the angiographic findings for 238 consecutive patients aged < or = 75 years who had been admitted to our hospital between 1 February 1995 and 1 February 1997 with inferior-wall AMI were retrospectively analyzed. The patients were divided into two groups according to the pattern of precordial ST-segment depression: LSTD+, ST-segment depression in leads V4-V6; and LSTD-, absence of this finding. All patients were treated according to current practice guidelines including with thrombolysis and revascularization interventions. RESULTS: The final study population included 217 patients; 83 were LSTD+ and 134 were LSTD-. All underwent coronary angiography within 30 days of the infarction. Compared with LSTD- patients, LSTD+ patients tended to be older (mean age 62.7 +/- 11.7 versus 58.3 +/- 9.6 years, P = 0.004), and had higher incidences of hypertension (39.8 versus 24.6%, P = 0.019) previous myocardial infarction (45.8 versus 20.1%, P = 0.0001) and congestive heart failure (21.7 versus 3.7%, P = 0.00008). Three-vessel CAD was much more common, and single-vessel CAD much less common, in the LSTD+ than in LSTD- group (62.7 versus 13.4% and 8.4 versus 50.7%, P < 0.00001 for both). Coronary-artery-bypass surgery and multivessel percutaneous coronary interventions (PCI) were used in treating 65.1% of the LSTD+ versus only 6.0% of the LSTD- patients (P < 0.00001), whereas single-vessel PCI was used in treating 71.6% of the LSTD- patients versus only 24.1% of the LSTD+ patients (P < 0.00001). Thus, the LSTD- pattern predicted single-vessel disease and single-vessel PCI only, whereas the LSTD+ pattern was predictive of multivessel CAD and of use of coronary-artery-bypass surgery or multivessel PCI (predictive values of 94.0 and 65.1%, respectively). CONCLUSIONS: Among patients with inferior-wall AMI, left precordial ST-segment depression predicts a very high prevalence of multivessel CAD and use of extensive revascularization interventions. The absence of this finding predicts nondiffuse CAD and lack of a need for extensive revascularization.

Thrombolysis is an effective and safe therapy in stuck bileaflet mitral valves in the absence of high-risk thrombi.

OBJECTIVES: We sought to evaluate the effectiveness and safety of thrombolytic therapy in stuck mitral bileaflet heart valves in the absence of high-risk thrombi. BACKGROUND: Current recommendations for the thrombolytic treatment of stuck prosthetic mitral valves are partially based on older valve models and inclusion of patients in whom high-risk thrombi were either ignored or not sought for. The feasibility and safety of thrombolysis in bileaflet models may be affected by the predilection of thrombi to catch the leaflet hinge. METHODS: We studied 12 consecutive patients (men/women = 5/7, age 58.8 +/- 14.9 years) who experienced one or more episodes of stuck bileaflet mitral valve over a 33-month period and received thrombolytic therapy with streptokinase, urokinase or tissue-type plasminogen activator. Transesophageal echocardiography was performed in all patients. Patients with mobile or large (>5 mm) thrombi were excluded. Functional class at initial episode was I-II in 4 patients (33.3%) and III-IV in 8 patients (66.6%). RESULTS: Patients receiving thrombolytic therapy achieved an overall 83.3% freedom from a repeat operation or major complications (95% confidence interval 51.6-97.9%). Minor bleeding occurred in three patients (25%) and allergic reaction in one (8.3%). Transient vague neurologic complaints, without subjective findings, occurred in four patients (33.3%). Three patients had one or more relapses within 5.2 +/- 3.1 months from the previous episode, and readministration of thrombolytics was successful. CONCLUSIONS: In clinically stable patients with stuck bileaflet mitral valves and no high-risk thrombi, thrombolysis is highly successful and safe, both in the primary episode and in recurrence. The best thrombolytic regimen is yet to be established.

Relation between evolutionary ST segment and T-wave direction and electrocardiographic prediction of mycardial infarct size and left ventricular function among patients with anterior wall Q-wave acute myocardial infarction who received reperfusion therapy.

In the prethrombolytic era it was found that infarct size and left ventricular ejection fraction could be predicted using the Selvester QRS score. We evaluated whether infarct size and left ventricular ejection fraction could be predicted by the predischarge QRS score in patients who had received reperfusion therapy and whether considering the configuration of the ST segments and T waves would increase the accuracy of these predictions. We evaluated 51 patients with first anterior wall myocardial infarction who had received reperfusion therapy and predischarge resting technetium-99m-sestamibi scan. The electrocardiograms recorded on the same day of the scan were analyzed for the QRS score and were divided into 3 groups: A, isoelectric ST and negative T waves; B, ST elevation (> or =0.1 mV) and negative T waves; and C, ST elevation (> or =0.1 mV) and positive T waves. Groups A, B, and C included 12, 23, and 16 patients, respectively. The myocardial perfusion defect extent increased from groups A to C (median 21%, 37%, and 43.5% in groups A, B, and C, respectively; p = 0.023). Similarly, left ventricular ejection fraction decreased (44%, 38%, and 34%, respectively; p = 0.042) from groups A to C. Overall, the correlation between the QRS score and the myocardial perfusion defect extent (rho 0.249; p = 0.08) and ejection fraction (rho -0.229; p = 0.11) was poor. A statistically significant correlation between myocardial perfusion defect size and QRS score was found only in group A (rho 0.599, p = 0.04). Among patients with anterior myocardial infarction who received reperfusion therapy, the predischarge QRS score was predictive of infarct size only in those in whom ST elevation resolved completely. In patients with residual ST elevation there was no correlation between QRS score and infarct size.

Correlation between the admission electrocardiogram and regional wall motion abnormalities as detected by echocardiography in anterior acute myocardial infarction.

We correlated ST elevation in various leads on admission and regional dysfunction in 132 patient with first anterior acute myocardial infarction using echocardiography. ST elevation in leads I and a VL and II, III and aVF was not associated with a specific pattern of regional dysfunction. Basal anterior and septal regional dysfunction were seen more often in patients with ST elevation in V1 (49 vs. 25%, p = 0.006; 35 vs. 17%, p = 0.048, respectively). Patients with ST elevation in V2 had more regional dysfunction of the apical inferior region (84 vs. 53%; p = 0.01). ST elevation in V5 and V6 was not associated with more apical or lateral wall motion abnormalities. ST elevation in lead V1 in anterior myocardial infarction is associated with a high incidence of regional dysfunction of the basal anterior, anteroseptal and septal regions.

The predischarge electrocardiographic pattern in anterior acute myocardial infarction: relation between evolutionary ST segment and T-wave configuration and prediction of myocardial infarct size and left ventricular systolic function by the QRS Selvester score.

Left ventricular systolic function, determined mainly by final infarct size, has a major influence on prognosis after acute myocardial infarction (MI). It was found that infarct size and left ventricular ejection fraction can be predicted using the Selvester QRS-score in patients not receiving reperfusion therapy. We assessed whether the predischarge QRS-score can be used for estimating infarct size and left ventricular ejection fraction in 51 patients with a first anterior MI who had received reperfusion therapy and whether considering the configuration of the ST-segments and T-waves will increase the accuracy of these predictions. All patients had received reperfusion therapy and had predischarge resting 99mTc-sestamibi scan. We determined the Selvester QRS score using the electrocardiograms performed on the same day of the scan. In addition, we divided the patients into 3 groups: A: isoelectric ST and negative T-waves (n = 12); B: ST elevation (> or =0.1 mV) and negative T-waves (n = 23); and C: ST elevation (> or =0.1 mV) and positive T-waves (n = 16). The myocardial perfusion defect extent increased from group A to C (28.5+/-16.4%, 39.4+/-14.8%, and 45.3+/-15.8% in groups A, B, and C. respectively; P = .022). Similarly, the left ventricular ejection fraction decreased (41.7+/-11.6%, 38.4+/-8.1%, and 32.0+/-9.7%, respectively; P = .042) from group A to C. Overall, the correlation between the QRS-score and the myocardial perfusion defect extent (Rho = 0.249; P = .08), and ejection fraction (Rho = -0.229; P = .11) was not good. A statistically significant correlation between the myocardial perfusion defect size and the QRS-score was found only in group A (Rho = 0.599, P = .04). In patients with a first anterior myocardial infarction who underwent reperfusion therapy, the predischarge QRS-score is predictive of infarct size only in those in whom ST elevation resolved completely. In patients with residual ST elevation the Selvester QRS-score is inaccurate in predicting infarct size and left ventricular ejection fraction upon discharge.

Coronary air embolism treated by bubble aspiration.

We describe a case of coronary air embolism following cardiac catheterization, with all the signs and symptoms of an acute coronary event. Thanks to the rapid and effective aspiration of the air bubble from the distal artery, blood flow was restored and the clinical picture was resolved.

Acute myocardial infarction following sildenafil citrate (Viagra) intake in a nitrate-free patient.

Since its introduction to the market in March 1997, sildenafil acetate (Viagra) has been prescribed to 1.7 million people. Sixteen men who were taking the drug have died, 7 of them during or soon after sexual activity. Most of these data have been derived from the media and not from the scientific literature. There is a general impression that cardiovascular complications of sildenafil occur mainly when the drug is taken concomitantly with nitrates. We describe a 65-year-old man with known coronary artery disease who had an acute myocardial infarction shortly after taking sildenafil and engaging an sexual activity. The patient had not been using nitrates. We suggest that the emotional arousal induced by Viagra, followed by the heavy physical exertion during sexual activity, triggers plaque rupture that leads to acute myocardial infarction.

Terminal QRS distortion on admission is better than ST-segment measurements in predicting final infarct size and assessing the Potential effect of thrombolytic therapy in anterior wall acute myocardial infarction.

We assessed predicting final infarct size (using predischarge Selvester score) by 3 electrocardiographic variables in 267 patients with first anterior wall acute myocardial infarction (AMI) undergoing (n = 86) or not undergoing (n = 181) thrombolysis. Patients with previous AMI or inverted T waves in leads with ST elevation were excluded. The sum (sigma) of ST elevation, the number of leads with ST elevation, and the initial electrocardiographic pattern were determined on the admission electrocardiogram (absence (QRS-) or presence (QRS+) of distortion of the terminal portion of the QRS in > or =2 leads (J point > or =0.5 of the R-wave amplitude in leads I, aVL, V4 to V6, or presence of ST elevation without S waves in leads V1 to V3). There was no association between sigmaST elevation and final infarct size in patients who did or did not receive thrombolytic therapy. Analysis of covariance showed that the number of leads with ST elevation (F = 19.6), thrombolysis (F = 25.2), and QRS+ initial pattern (F = 19.5) were all associated with final infarct size (p <0.0001 for all). Among patients who did not receive thrombolytic therapy, the average Selvester score was 19.7+/-9.9 for the QRS- patients and 26.1+/-10.4 for the QRS+ patients (p = 0.02). Among patients who received thrombolytic therapy, the average Selvester score was 11.7+/-9.8 for the QRS- patients and 24.2+/-10.1 for the QRS+ patients (p <0.0001). Thrombolysis reduced final Selvester score only in the QRS- group (p <0.00001), but not in the QRS+ group (p = 0.45). It is concluded that (1) final Selvester score in anterior wall AMI can be predicted by the number of leads with ST elevation, the initial electrocardiographic pattern, and thrombolysis, and (2) thrombolysis reduces final Selvester score only in patients with QRS- pattern.

Perforation of the right ventricular free wall by an active fixation transvenous cardioverter defibrillator lead.

A 58-year-old patient with dilated cardiomyopathy underwent implantable cardioverter defibrillator (ICD) implantation. The postoperative course was complicated by perforation of the right ventricular free wall by the active fixation transvenous ICD lead. The type of ICD lead and the type of organic heart disease are apparently important risk factors for perforation.

Relation between QT dispersion and slow intraventricular conduction in patients with acute anterior wall myocardial infarction.

BACKGROUND: QT dispersion has been proposed as a simple, noninvasive measure for identifying patients at risk of postinfarction arrhythmia. It is assumed to reflect nonuniform ventricular repolarization, which, in turn, may result from regional differences in repolarization time as well as from localized activation delay. The aim of this study was to examine the relation between QT dispersion and intraventricular conduction abnormalities in patients with acute anterior wall myocardial infarction. METHODS AND RESULTS: Standard 12-lead electrocardiographic and 12-lead signal-averaged electrocardiographic recordings were performed in 25 patients with a first Q-wave anterior wall myocardial infarction. Measures calculated by using the 6 precordial (V1 through V6) leads for QT dispersion were (1) difference between maximum and minimum QT and QTc intervals and (2) standard deviation of QT and QTc intervals. Measures calculated from the signal-averaged electrocardiogram were (1) maximum filtered QRS duration; (2) mean; and (3) standard deviation of filtered QRS duration. No relation was found between any measure of filtered QRS duration and that of QT dispersion by using linear correlation analysis. Similarly, no significant association was demonstrated between the filtered QRS duration and corresponding QT interval measurements (total 131 leads). CONCLUSIONS: The lack of correlation between signal-averaged electrocardiogram indexes of slow intraventricular conduction and electrocardiogram variables of QT dispersion suggests an independent predictive value for the 2 methods in identifying patients at risk of postinfarction arrhythmia. This suggestion is further supported by the finding that altered activation sequence is an unlikely mechanism of QT dispersion in patients with acute myocardial infarction, as indicated by the lack of association between the filtered QRS duration and corresponding QT interval measurements.