Marcelo E. Helguera

Long-term performance of endocardial pacing leads.

To assess the performance of endocardial pacemaker leads and to identify factors associated with structural lead failure, medical records of 2,611 endocardial pacing leads (in 1, 5W patients) implanted between 1980 and 1991, having at least 1 month of follow‐up, were reviewed. Leads without structural failure had normal function at the last follow‐up date, or were discontinued for reasons other than structural failure (patient death, infection, dislodgment, lead‐pacemaker incompatibility, operative complication, or abandonment by telemetry not related to failure). Leads with suspected structural failures were invasively or noninvasively disconnected because of clinical malfunction (loss of capture or sensing, oversensing, elevated thresholds, or skeletal muscular stimulation). Leads with verified structural failures met the criteria for suspected lead failure and also had a visible defect seen in the operating room or on chest roentgenograms, a change in the impedance interpreted by the physician as lead disruption, or a manufacturers return product report that confirmed structural failure. Variables analyzed included patients’ age and gender, paced chamber, venous access, insulation materials, fixation mechanism, coaxial design, polarity, and different lead models. The cumulative lead survival at 5 and 10 years were 97.4% and 92.9%, respectively, for suspected failures; and 98.7% and 97.3%, respectively, for verified failures. Leads in older patients (≥ 65 years old), and leads in atrial position had fewer verified failures (P = 0.014 and P = 0.007, respectively). Unipolar leads also tended to perform better according to the verified definition (P = 0.07). The lead Medtronic 4012 had more suspected (P < 0.05) and more verified failures (P < 0.01), the lead CPI 4010 had more verified failures (P < 0.05) than the entire group of ventricular leads. Conclusions: Endocardial pacing leads implanted in atrial position, and implanted in older patients (> 65 years old) seems to have better long‐term survival. Some lead models (Medtronic 4012 and CPI 4010) had poor survival rates, that could not be explained by the analyzed variables. The expected performance of endocardial pacing leads varies according to how failure is defined.

Pacing Lead Survival: Performance of Different Models

Recent reports have shown poor survival of some leads currently in use. Long‐term survival analysis of 2,444 leads (1,059 atrial and 1,385 ventricular) implanted in this institution since January 1980, and having at least 1 month of follow‐up was performed. The survival of 123 different models was compared with the average survival of all the leads implanted in the corresponding chamber. Failure was defined as inactivation of the lead (electrical abandonment, explant, or cap) due to insulator and/or conductor fracture. Results: The mean follow‐up was 33 ± 32 months. The cumulative survival for different atrial lead models was consistent with the average performance in the atrium. No atrial lead showed better or worse survival compared to the others. In the ventricular group, the Medtronic 4012 lead showed statistically significant poorer survival (P = 0.01) compared with the average survival of the ventricular leads. The Cardiac Pacemakers, Inc. (CPI) 4010 lead showed a nonsignificant (P = 0.12) worse performance than the average for ventricular leads. Conclusions: (1) The Medtronic 4012 had a significantly poorer performance than the rest of the leads. A trend in similar direction was found for the CPI 4010, also in the ventricular group; (2) Atrial lead models showed a stable survival; and (3) Frequent follow‐up is required for some leads, especially in pacemaker dependent patients.

Influence of amiodarone on QT dispersion in patients with life-threatening ventricular arrhythmias and clinical outcome

UNLABELLED Increased QT dispersion, defined as the difference between the maximum and minimum QT interval on the standard 12-lead electrocardiogram is assumed to reflect regional inhomogeneity of ventricular repolarization and has been shown to be associated with an increased risk of arrhythmic events. The purpose of the present study is to examine the influence of amiodarone on QT dispersion in patients with life-threatening ventricular arrhythmias and to evaluate the predictive value of QT dispersion after amiodarone therapy for further arrhythmic events. ECGs were obtained in 47 patients 1-2 days before and 6-8 weeks after amiodarone was started. All patients had coronary artery disease with a mean EF of 34 +/- 14%. The QT interval was measured in each lead of a digitized ECG displayed on a high resolution monitor (250 mm s-1). Amiodarone therapy resulted in a significant increase in the maximal QTc interval (476 +/- 44 to 505 +/- 44 ms, p < 0.001). However, measurement of QT dispersion (70 +/- 34 vs 73 +/- 29 ms) and Qtc dispersion (78 +/- 37 vs 77 +/- 31 ms) revealed no significant difference before and after amiodarone. During a one year follow-up period 26 patients were free of arrhythmic events and 7 patients developed further arrhythmic events. The remaining 14 patients were excluded from the one year follow-up analysis because of drug discontinuation (n = 8), death due to heart failure (n = 1), medical intervention (n = 3) and incomplete follow-up (n = 2). No measure of QT dispersion was predictive of recurrent arrhythmic events during treatment with amiodarone. CONCLUSION Treatment with amiodarone results in significant QT prolongation without altering QT dispersion. Measurements of QT dispersion were not predictive of amiodarone efficacy in this patient population.

Memory T Waves After Radiofrequency Catheter Ablation of Accessory Atrioventricular Connections in Wolff-Parkinson-White Syndrome

Generalized, extensive electrical repolarization abnormalities, represented by negative or abnormally peaked T waves, are frequently observed after radiofrequency catheter ablation of overt accessory atrioventricular (AV) connections in Wolff-Parkinson-White (WPW) syndrome. Two mechanisms have been proposed to explain these changes: subendocardial injury, secondary to the application of radiofrequency lesions, and memory T waves. The purpose of this study is to evaluate the electrocardiographic (ECG) changes in patients with overt and concealed accessory AV connections after ablation. Fifty-one patients with accessory AV connections who underwent successful radiofrequency ablation were included in the study. Twenty-four patients with clear, manifest, and permanent preexcitation (group 1) were compared with 27 patients with concealed accessory AV connections (group 2). Electrocardiograms were obtained in all patients before ablation, shortly after ablation (within 4 hours), and late after ablation (6 weeks). The frontal and horizontal QRS-T angles in the ECGs, number of lesions, total Joules applied, total peak creatine kinase, and total peak creatine kinase-MB units were compared in both groups. Of the 24 patients with overt accessory AV connections, 23 (95.8%) demonstrated repolarization abnormalities in the ECG shortly after the procedure that reverted almost completely at 6 weeks. Of the 27 patients with concealed accessory AV connections, only 2 (7.4%) demonstrated repolarization abnormalities after the ablation (P < .0001). The persistence of an abnormal QRS-T angle immediately after ablation in patients with overt accessory AV connections is caused by an abnormality in the T wave axis, opposite to the direction of the normal QRS axis.(ABSTRACT TRUNCATED AT 250 WORDS)

Long‐Term Performance of Epimyocardial Pacing Leads in Adults: Comparison with Endocardial Leads

The long‐term performance of epimyocardiaJ pacing leads in children is well established, but few studies have analyzed the performance in adults. This issue has clinical relevance in view of the increased use of epimyocardial leads with implantable cardioverter defibrillator and antitachycardia pacing systems. We analyzed 93 epimyocardial pacing “systems” (121 leads: 65 unipolar, 28 bipolar) in adult patients (age 57 ± 16 years), implanted since January 1980. Two different models were studied: Medtronic 4951 “Stab–on” (n = 35) and Medtronic 6917/6917A “Screw‐in” (n = 58). A control group was created by randomly matching each epimyocardial system with two endocardial leads, according to age and year of implant. Epimyocardial and endocardial leads were followed‐up for 44 ± 35 and 43 ± 35 months, respectively (P = NS). Freedom from failure for epimyocardial leads was 0.91 (95% Confidence Interval [95% CI] = 0.82 to 0.96) at 5 years, and 0.91 f95% CI = 0.69 to 0.98) at 10 years. No difference was found between the two analyzed models. Freedom from failure for endocardial leads was 0.97 (95% CI = 0.93 to 0.99) and 0.90 (95% CI = 0.61 to 0.97) at 5 and 10 years, respectively. Epimyocardial Jeads had a significantly poorer short‐term survival than endocardiaJ leads, secondarily to earlier “technique related” failures (P = 0.03; relative riskc 3.0; Wilcoxon test). However, overall long‐term performance was similar to endocardial leads. Epimyocardial pacing leads, meticulously implanted and tested, have a long‐term performance similar to endocardial pacing leads.

Cardiovascular Emergencies in Cruise Ship Passengers

More than 10 million people, many elderly and likely to harbor cardiovascular (CV) disease, embark on cruise ship travel worldwide every year. The clinical presentation and outcome of CV emergencies presenting during cruise ship travel remain largely unknown. Our department provides contracted cardiology consultations to several large cruise lines. We prospectively maintained a registry of all such consultations during a 2-year period. One hundred consecutive patients were identified (age 66 +/- 14 years, range 18 to 90, 76% men). The most common symptom was chest pain (50%). The most common diagnosis was acute coronary syndrome (58%; ST elevation in 21% and non-ST elevation in 37%). On-board mortality was 3%. Overall, 73% of patients required hospital triage. Of the 25 patients triaged to our institution, 17 underwent a revascularization procedure. One patient died. Ten percent of patients had cardiac symptoms in the days or weeks before boarding; all required hospital triage. Access to a baseline electrocardiogram would have been clinically useful in 23% of cases. In conclusion, CV emergencies, such as acute coronary syndrome and heart failure, are not uncommon on cruise ships. They are often serious, requiring hospital triage and coronary revascularization. A pretravel medical evaluation is recommended for passengers with a cardiac history or a high-risk profile. Passengers should be encouraged to bring a copy of their electrocardiogram on board if abnormal. Cruise lines should establish mechanisms for prompt consultation and triage.

Postcardiac injury syndrome following transvenous pacer or defibrillator insertion: CT imaging and review of the literature.

Postcardiac injury syndrome (PCIS) is a frequent clinical entity developing as a complication of cardiac procedures. Some of these may be only minor procedures, such as the insertion of permanent pacer or defibrillator devices. The purpose of this article is to review and illustrate its common imaging findings. PCIS is expected to occur in approximately 1%-2% of patients after pacer or defibrillator device placement. The mechanism of pericarditis following implantation is unclear, but it may involve a direct irritation of the pericardium by minimally protruding electrodes, low-grade bleeding with hemorrhagic pericarditis, and a late autoimmune or inflammatory response to those insults. Radiologists may detect findings that in the appropriate clinical setting should raise the possibility of PCIS. On chest x-ray, the findings include the presence of a pericardial or pleural effusion or both. Computed tomography, in addition to having better characterization capabilities of the pericardial or pleural effusion or both, may also accomplish the diagnosis of lead perforation. Although typically rather benign, PCIS may result in significant morbidity and potential mortality due to arrhythmias, noncardiac pulmonary edema, and cardiac tamponade. Therefore, its early detection is of clinical importance.

Shortness of breath after AV ablation: case of left phrenic nerve palsy

Phrenic nerve palsy has been recognized as a complication of catheter ablation with a prevalence of 0.11–0.48% after atrial fibrillation ablation, independent of the type of ablation catheter or energy source, likely due to the anatomical relationship of the nerves. This report describes a case of new onset of shortness of breath (SOB) due to left diaphragm paralysis following transcatheter radiofrequency ablation in a patient with underlying chronic obstructive pulmonary disease.

Thirty years of blackouts: a case report of swallow syncope.

Deglutition syncope has been demonstrated in isolated case reports, the first being described over 50 years ago. It is thought to be caused by a hypersensitive vagotonic reflex in response to esophageal dilation after swallowing. It can cause syncope due to complete atrioventricular (AV) block and acute reduction of cardiac output. Although rare, its lethality is worthy of discussion, as early recognition can offer complete treatment with placement of a pacemaker. A 54-year-old man presented with 30 years of lightheadedness and syncope, followed by disorientation and tremors, after eating sandwiches or drinking carbonated beverages. He initially was evaluated by a neurologist. Work-up included cardiac 2D transthoracic echocardiogram, electroencephalogram, swallow stud, pulmonary function tests, electrocardiogram, and cardiac stress testing. All tests were within normal limits, and it was determined that he was suffering from convulsive syncope and deglutition syncope. Referral to the cardiac electrophysiology department with tilt-table testing accompanied by swallow evaluation was then recommended. The tests demonstrated marked vagal response resulting in sinus bradycardia with second-degree AV block and pauses up to 3.5 seconds. Patient experienced near syncope. A rate-responsive, dual-chamber Boston Scientific pacemaker with DDDR programming was implanted. Patient has remained asymptomatic at follow-up.

Clinical presentation off endocardial pacing lead malfunction

This study highlights the wide spectrum of manifestation of pacing lead malfunction. Patients judged to be pacer dependent or in whom ventricular lead malfunction is suspected, and patients with severe symptoms before pacemaker implantation, should be considered at high risk for the development of hemodynamic compromise; prompt hospital admission and pacing lead replacement should be performed.