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Stephen C Hammill

Publications and source records attributed to Stephen C Hammill.

At least 19 recordsLinked to original sources
PubMed2006

Electrocardiography cannot reliably differentiate transient left ventricular apical ballooning syndrome from anterior ST-segment elevation myocardial infarction.

OBJECTIVE: The presentation and electrocardiographic (ECG) characteristics of transient left ventricular apical ballooning syndrome (TLVABS) can be similar to that of anterior ST-segment elevation myocardial infarction (STEMI). We tested the hypothesis that the ECG on presentation could reliably differentiate these syndromes. SUBJECTS AND METHODS: Between January 1, 2002 and July 31, 2004, we identified 18 consecutive patients with TLVABS who were matched with 36 subjects presenting with acute anterior STEMI due to atherothrombotic left anterior descending coronary artery occlusion. RESULTS: All patients with TLVABS were women (mean age, 72.0 +/- 13.1 years). The heart rate, PR interval, QRS duration, and corrected QT interval were similar between groups. Distribution of ST elevation was similar, but patients with anterior STEMI exhibited greater ST elevation. Regressive partitioning analysis indicated that the combination of ST elevation in lead V2 of less than 1.75 mm and ST-segment elevation in lead V3 of less than 2.5 mm was a suggestive predictor of TLVABS (sensitivity, 67%; specificity, 94%). Conditional logistic regression indicated that the formula: (3 x ST-elevation lead V2) + (ST-elevation V3) + (2 x ST-elevation V5) allowed possible discrimination between TLVABS and anterior STEMI with an optimal cutoff level of less than 11.5 mm for TLVABS (sensitivity, 94%; specificity, 72%). Patients with TLVABS were less likely to have concurrent ST-segment depression (6% vs 44%; P = .003). CONCLUSIONS: Women presenting with TLVABS have similar ECG findings to patients with anterior infarct but with less-prominent ST-segment elevation in the anterior precordial ECG leads. These ECG findings are relatively subtle and do not have sufficient predictive value to allow reliable emergency differentiation of these syndromes.

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PubMed2006

Relapse and mortality following cardioversion of new-onset vs. recurrent atrial fibrillation and atrial flutter in the elderly.

AIMS: Trials of rate control vs. rhythm control for atrial fibrillation or flutter included few patients with new-onset arrhythmia. Our objective was to assess the relapse rate and the effect of the relapse of new-onset atrial arrhythmias on mortality after direct-current cardioversion (DCCV). METHODS AND RESULTS: A cohort of 351 patients with atrial fibrillation (new onset in 179) and 126 patients with atrial flutter (new onset in 78) was followed-up after DCCV. Cox proportional hazard models were used. Median age was 74.6 years. Mean follow-up for relapse was 7.7 months; for death, 29.4 months. Patients with new-onset atrial flutter [adjusted hazard ratio (HR) = 1] were more likely to maintain sinus rhythm than the patients with recurrent atrial flutter (adjusted HR = 2.5, P < 0.01), new-onset atrial fibrillation (adjusted HR = 2.4, P < 0.01), or recurrent atrial fibrillation (adjusted HR = 2.7, P < 0.01). Patients with new-onset atrial fibrillation were as likely to have relapses as patients with recurrent atrial fibrillation or flutter. Relapse of atrial arrhythmia after DCCV was associated with increased mortality (adjusted HR= 3.1, P < 0.01). CONCLUSION: DCCV is more successful in maintaining sinus rhythm in patients with new-onset atrial flutter than in patients with new-onset atrial fibrillation. Relapse of atrial arrhythmia after cardioversion is associated with increased mortality.

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PubMed2006

The effect of patient sex on recurrence of atrial fibrillation following successful direct current cardioversion.

BACKGROUND: The effect of patient sex on recurrence of atrial fibrillation after a successful direct current cardioversion is unknown. METHODS: This prospective study included 773 patients (486 [63%] men and 287 [37%] women) undergoing successful direct current cardioversion of atrial fibrillation between May 2000 and July 2003. Patient characteristics at presentation were recorded. The primary end point was the time between cardioversion and the first documented recurrence of arrhythmia. RESULTS: At presentation, women were older and had a higher prevalence of hypertension and valvular disease compared with men. In addition, women had worse mechanical left atrial appendage function. Arrhythmia recurrence was more prevalent in women (50.0% at 1 year compared with 43.4% in men, and 75.8% at 2 years compared with 67.0% in men; P = .03). On the basis of multivariate analysis, patient sex was a significant predictor of arrhythmia recurrence. There was no significant difference in overall mortality between men and women. CONCLUSIONS: Women were more likely than men to have recurrence of atrial fibrillation after successful direct current cardioversion. Patient sex should be taken into account with other clinical factors when making the decision about cardioversion for atrial fibrillation.

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PubMed2005

Effect of atrial fibrillation pattern on survival in a community-based cohort.

The clinical presentation of recurrent atrial fibrillation (AF) has been categorized into 3 general patterns: paroxysmal, persistent, and permanent AF. This community-based cohort study characterized the effect of the AF pattern on survival. Community residents in Olmsted County, Minnesota, with electrocardiographically proven new-onset AF during 1996 and 1997 were retrospectively identified and prospectively followed. Observed survival was estimated using the Kaplan-Meier method and compared with the expected survival. Log-rank tests were used for group comparisons. The association between the baseline variables and mortality was assessed using Cox proportional hazards models. Of 270 patients (mean +/- SD age 73 +/- 14 years; 148 men [55%]), 143 had paroxysmal AF, 40 had persistent AF, and 87 had permanent AF. The cohort's observed survival was significantly worse than expected (p <0.001). The factors associated with increased mortality included older age, concomitant heart failure, and concomitant chronic obstructive pulmonary disease (all p <0.001). Permanent AF was associated with higher mortality than paroxysmal AF (hazard ratio 1.6, 95% confidence interval 1.1 to 2.3). Persistent AF was associated with better survival (hazard ratio 0.3, 95% confidence interval 0.1 to 0.8). In conclusion, survival among patients with persistent AF was significantly better than that among patients with paroxysmal AF or permanent AF. The ability to maintain sinus rhythm may be associated with better survival.

Age Factors↗
PubMed2005

Relation of QRS duration on the surface 12-lead electrocardiogram with mortality in patients with known or suspected coronary artery disease.

The aim of this study was to assess the relation between QRS duration and mortality in patients with known or suspected coronary artery disease, after adjustment for myocardial functional abnormalities, as assessed by exercise echocardiography. We studied 4,033 patients (age 62 +/- 12 years; 2,360 men, 18% with previous myocardial infarction) who underwent symptom-limited exercise echocardiography. The QRS duration was electronically measured from the 12-lead electrocardiogram. The incremental value of the QRS duration for predicting mortality was assessed by adding the QRS duration at the end of each of these modeling steps: clinical data, exercise electrocardiographic, and exercise echocardiographic variables. The QRS duration correlated positively with age, the wall motion score index at rest, and percentage of ischemic segments and negatively with workload (p = 0.0001). Of the 4,033 patients, 252 died during a median follow-up of 3 years. The QRS duration was univariately associated with an increased risk of death (relative risk 8.5, 95% confidence interval CI 4.4 to 16.4, p <0.0001). In an incremental multivariate model, the clinical predictors of mortality were age, male gender, previous infarction, and diabetes mellitus (chi-square 122). Workload was incremental to clinical data in the exercise test model (chi-square 193, p <0.0001). The exercise wall motion score index was incremental to both models (chi-square 211, p <0.001). The QRS duration was associated with an incremental risk of death when added to the clinical model (chi-square 133, p = 0.009), exercise test model (chi-square = 203, p = 0.002), and echocardiographic model (chi-square = 216, p = 0.03). A QRS duration > or =105 ms best identified patients at increased risk. In conclusion, QRS duration is associated with an increased risk of death, even after adjustment for clinical factors, exercise capacity, left ventricular function, and exercise-induced myocardial ischemia.

Blood Pressure↗
PubMed2005

Score indices for predicting electrophysiologic outcomes in patients with unexplained syncope.

INTRODUCTION: Our ability to predict a positive electrophysiologic (EP) study in the evaluation of unexplained syncope is suboptimal. AIMS: In patients with unexplained syncope, we defined clinical predictors of bradyarrhythmia and ventricular tachycardia (VT) diagnosed during EP study, constructed diagnostic score indices for bradyarrhythmia and VT, and evaluated the predictive power of each score index. METHODS: All patients evaluated in the Arrhythmia Clinic for unexplained syncope from January 1, 1996, through December 31, 1998, were identified and enrolled in the study. Five hundred eight patients (325 [64%] men; mean+/-SD age, 64+/-17 years) underwent EP testing. We analyzed elements from historical data and noninvasive laboratory findings as predictors of bradyarrhythmia and VT diagnosed on EP study. RESULTS: Fifty-eight patients (11%) had sinus node dysfunction, 94 (19%) had atrioventricular (AV) node disease, 92 (18%) had His-Purkinje system disease, and 101 (20%) had VT. Models were fit using logistic regression analysis. Predictors were assigned weighted scores, and a score index was formulated. The area under the curve associated with sinus node dysfunction, AV node disease, His-Purkinje system disease, and VT models was 0.64, 0.60, 0.84, and 0.60, respectively. CONCLUSIONS: We have constructed diagnostic score indices for EP outcomes of bradyarrhythmia and VT in syncope. Of all the score indices, the model for His-Purkinje system disease has the highest predictive power.

Arrhythmias, Cardiac↗
PubMed2005

Comparative efficacy of monophasic and biphasic waveforms for transthoracic cardioversion of atrial fibrillation and atrial flutter.

BACKGROUND: Transthoracic cardioversion fails to restore sinus rhythm in 6% to 33% of patients with atrial fibrillation. This study sought to determine the relative efficacy of biphasic waveforms compared with monophasic waveforms in the treatment of atrial arrhythmias. METHODS: A total of 912 patients underwent 1022 transthoracic cardioversions between May 2000 and December 2001. A monophasic damped sine waveform was used in the first 304 cases, and a rectilinear biphasic defibrillator was used in the next 718 cases. RESULTS: Use of a biphasic waveform was associated with 94% success in conversion to sinus rhythm compared with 84% with a monophasic waveform (P < .001). The cumulative energy required to restore sinus rhythm was lower with biphasic shocks in both atrial fibrillation and atrial flutter groups (554 +/- 413 J for monophasic vs 199 +/- 216 J for biphasic shocks in the atrial fibrillation group, P < .001; 251 +/- 302 J vs 108 +/- 184 J, respectively, in the atrial flutter group, P < .001). In a multivariate analysis, use of a biphasic shock was associated with a 3.9-fold increase in success of cardioversion. CONCLUSION: When used to cardiovert atrial arrhythmias, the rectilinear biphasic waveform was associated with higher success rates and lower cumulative energies than the monophasic damped sine waveform.

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PubMed2005

Prospective, randomized comparison of two biphasic waveforms for the efficacy and safety of transthoracic biphasic cardioversion of atrial fibrillation.

OBJECTIVES: The purpose of this study was to determine if there is a difference in commercially available biphasic waveforms. BACKGROUND: Although the superiority of biphasic over monophasic waveforms for external cardioversion of atrial fibrillation (AF) is established, the relative efficacy of available biphasic waveforms is less clear. METHODS: We compared the effectiveness of a biphasic truncated exponential (BTE) waveform and a biphasic rectilinear (BR) waveform for external cardioversion of AF. Patients (N = 188) with AF were randomized to receive transthoracic BR shocks (50, 75, 100, 120, 150, 200 J) or BTE shocks (50, 70, 100, 125, 150, 200, 300, 360 J). Shock strength was escalated until success or maximum energy dose was achieved. If maximum shock strength failed, patients received the maximum shock of the opposite waveform. Analysis included 141 patients (71 BR, 70 BTE; mean age 66.5 +/- 13.7. Forty-seven randomized patients were excluded because of flutter on precardioversion ECG upon blinded review (n = 25), presence of intracardiac thrombus (n = 7), or protocol deviation (n = 15). Groups were similar with regard to clinical and echocardiographic characteristics. RESULTS: The success rate was similar for the two waveforms (93% BR vs 97 BTE, P = .44), although cumulative selected and delivered energy was less in the BTE group. Only AF duration was significantly different between successful and unsuccessful patients. No significant complications occurred. CONCLUSIONS: Biphasic waveforms were very effective in transthoracic cardioversion of AF, and complication rates were low. No significant difference in efficacy was observed between BR and BTE waveforms. Impedance was not an important determinant of success for either biphasic waveform.

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PubMed2005

Grade 3 ischemia on the admission electrocardiogram predicts rapid progression of necrosis over time and less myocardial salvage by primary angioplasty.

BACKGROUND: Among patients with ST-elevation acute myocardial infarction, those with terminal QRS distortion (grade 3 ischemia) have higher mortality and larger infarct size (IS) than patients without QRS distortion (grade 2 ischemia). METHODS: We assessed the relation of baseline electrocardiographic ischemia grades to area at risk (AR) and myocardial salvage [100 (AR-IS)/AR] in 79 patients who underwent primary angioplasty for first ST-elevation acute myocardial infarction and had technetium Tc 99m sestamibi single-photon emission computed tomography before angioplasty (AR) and at predischarge (IS). Patients were classified as having grade 2 ischemia (ST elevation without terminal QRS distortion in any of the leads, n = 48), grade 2.5 ischemia (ST elevation with terminal QRS distortion in 1 lead, n = 16), or grade 3 ischemia (ST elevation with terminal QRS distortion in >2 adjacent leads, n = 15). RESULTS: Time to treatment was comparable among groups. AR was comparable among groups (38% +/- 20%, 33% +/- 23%, and 34% +/- 23%, respectively; P = .70). There were no differences among groups in residual myocardial perfusion (severity index 0.28 +/- 0.12, 0.29 +/- 0.16, and 0.30 +/- 0.15 in grades 2, 2.5, and 3 ischemia, respectively; P = .97). In contrast, there was a trend toward lower myocardial salvage (45% +/- 32%) in the grade 3 group than in the grade 2 (65% +/- 33%) and grade 2.5 (65% +/- 40%) groups ( P = .16). Salvage was dependent on time only in the grade 3 group. Spearman rank correlation coefficients between time to treatment and percentage salvage were 0.003 ( P = .99), -0.24 ( P = .38), and -0.63 ( P = .022) for grades 2, 2.5, and 3, respectively. CONCLUSIONS: Patients with grade 3 ischemia have rapid progression of necrosis over time and less myocardial salvage. This admission pattern is a predictor of myocardial salvage by primary angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed2005

Outcomes after ventricular fibrillation out-of-hospital cardiac arrest: expanding the chain of survival.

Coronary heart disease is the most common cause of death in the United States, with ventricular fibrillation (VF) the most common initial rhythm when cardiac disease causes arrest. Survival after VF out-of-hospital cardiac arrest (OHCA) depends on a sequence of events called the chain of survival, which Includes rapid access to emergency medical services, cardiopulmonary resuscitation, defibrillation, and advanced care. Because of widespread implementation of defibrillation programs, more patients survive VF OHCAs, making subsequent care of these patients important. Early hospitalization must focus on potential neurologic injury and therapy targeted at the underlying cardiac disease and antiarrhythmic therapy for long-term secondary prevention of sudden death. Attention to certain cohorts who are at high risk despite their underlying disease, such as women and elderly patients, is necessary. These cohorts may have the greatest response to short-term and long-term therapies for cardiac rehabilitation. With these approaches, long-term survival and quality of life after VF OHCA are favorable. Broadening the focus of the chain of survival to include in-hospital and long-term care will further improve favorable outcomes achieved in an early defibrillation program.

Heart Arrest↗
PubMed2005

Recurrence of atrial tachyarrhythmias in implantable cardioverter-defibrillator recipients.

BACKGROUND: Because the natural history of atrial tachyarrhythmia (AT) is not known in patients with implantable cardioverter-defibrillators (ICDs) but without device-based atrial therapies, we aimed to describe the characteristics and recurrence of AT in such patients. METHODS: In this multicenter trial, 269 patients with standard indications for ICD placement and 2 episodes of AT in the preceding year received a dual-chamber ICD capable of logging AT. Patients were randomly assigned to 3-month periods of atrial therapies "on" or "off." This analysis considered only the 118 patients with atrial therapies programmed off at ICD placement. RESULTS: Fifty-eight patients (49%) had at least 1 AT episode longer than 1 minute, and 21 (18%) had at least 1 prolonged episode (>24 hours). The median episode frequency for each patient (episodes per month) was 1.8 episodes longer than 1 minute, 0.8 longer than 1 hour, and 0 longer than 24 hours. The median AT burden was 12.2 hours per month. CONCLUSIONS: Patients with standard ICD indications and history of AT have infrequent episodes, frequent short episodes, or prolonged episodes of AT-atrial fibrillation. However, the clinical characteristics examined did not distinguish among the groups. Improved diagnostic tools may help identify patients at risk for development of AT, thereby allowing specific therapies to be targeted to each group of patients.

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PubMed2005

Use of advanced mapping systems to guide ablation in complex cases: experience with noncontact mapping and electroanatomic mapping systems.

OBJECTIVE: This report describes our experience with noncontact mapping and electroanatomic mapping in complex ablations, which are defined as ablations done after failure of conventional ablation. MATERIAL AND METHODS: Patients were included (N = 68; 49% with structural heart disease) in whom previous ablation failed and in whom a second procedure was done with advanced mapping. Non-contact mapping was used in 17 patients, electroanatomic mapping in 36, and both noncontact and electroanatomic mapping in 15. Arrhythmias included focal atrial tachycardia (n = 16), reentrant atrial tachycardia (n = 14), right ventricular outflow tachycardia (n = 10), post-myocardial infarction ventricular tachycardia (n = 9), and others (n = 19). RESULTS: Acute success at the second ablation was achieved in 79% of patients. At 20 +/- 9 months after the procedure, 69% of these patients reported having significantly fewer symptoms than before the second ablation, and 51% were free of symptoms. Only 16% were using antiarrhythmic medications. Complications included a small pericardial effusion in two patients, hypotension in one patient, and a femoral pseudoaneurysm in another. CONCLUSIONS: Advanced mapping is a useful and safe adjunct for catheter ablation after ablation has failed in patients with complex substrate.

Arrhythmias, Cardiac↗
PubMed2005

Noninvasive assessment of acute changes in atrial electrophysiology after cardioversion by signal-averaged P-wave electrocardiography.

BACKGROUND: Atrial remodeling secondary to atrial fibrillation (AF) may be important in the arrhythmogenic process. Unfortunately, the study of electrophysiologic remodeling in humans has been limited by the invasive nature of most tests of electrophysiologic characteristics. We sought to determine whether changes in atrial electrophysiology occur acutely (within the first hour) after cardioversion and whether these changes could be detected noninvasively by measuring the signal-averaged P-wave. METHODS: The filtered P-wave duration (FPD) was measured by signal-averaged electrocardiography (ECG) at 20 and 60 minutes after cardioversion in 46 patients with AF, and the difference between the two values was calculated. The root-mean-square voltage of the terminal 40 ms of the signal-averaged P-wave at 20 and 60 minutes and the difference between them were also determined. RESULTS: The FPD at 20 minutes was significantly different from that at 60 minutes (153.0 +/- 19.1 vs 159.7 +/- 24.8 ms; P = 0.02). In a univariate linear regression model, none of the clinical variables studied was significantly associated with the change in FPD. The root-mean-square voltage at 20 minutes was not significantly different from that at 60 minutes (5.8 +/- 3.0 vs 5.5 +/- 2.7; P = 0.14). CONCLUSIONS: We conclude that significant changes in atrial electrophysiology occur within the first hour after cardioversion of AF. These changes can be detected by measuring the FPD.

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