Beat Schaer

Necessity for Surgical Revision of Defibrillator Leads Implanted Long-Term Causes and Management

Background— Defibrillator lead malfunction is a potential long-term complication in patients with an implantable cardioverter-defibrillator (ICD). The aim of this study was to determine the incidence and causes of lead malfunction necessitating surgical revision and to evaluate 2 approaches to treat lead malfunction. Methods and Results— We included 1317 consecutive patients with an ICD implanted at 3 European centers between 1993 and 2004. The types and causes of lead malfunction were recorded. If the integrity of the high-voltage part of the lead could be ascertained, an additional pace/sense lead was implanted. Otherwise, the patients received a new ICD lead. Of the 1317 patients, 38 experienced lead malfunction requiring surgical revision and 315 died during a median follow-up of 6.4 years. At 5 years, the cumulative incidence was 2.5% (95% confidence interval, 1.5 to 3.6). Lead malfunction resulted in inappropriate ICD therapies in 76% of the cases. Implantation of a pace/sense lead was feasible in 63%. Both lead revision strategies were similar with regard to lead malfunction recurrence (P=0.8). However, the cumulative incidence of recurrence was high (20% at 5 years; 95% confidence interval, 1.7 to 37.7). Conclusions— ICD lead malfunction necessitating surgical revision becomes a clinically relevant problem in 2.5% of ICD recipients within 5 years. In selected cases, simple implantation of an additional pace/sense lead is feasible. Regardless of the chosen approach, the incidence of recurrent ICD lead-related problems after lead revision is 8-fold higher in this population.

Death Without Prior Appropriate Implantable Cardioverter-Defibrillator Therapy A Competing Risk Study

Background— Implantable cardioverter-defibrillators (ICDs) improve survival in selected patients with left ventricular systolic dysfunction in randomized trials. Competing death without prior appropriate ICD therapy might preclude benefit from ICD implantation in a less selected routine-care population. Methods and Results— We selected all patients with ischemic or dilated cardiomyopathy with an ICD implanted for primary or secondary prevention from a single-center prospective registry between 1994 and 2006. The end point was time to first appropriate ICD therapy/confirmed ventricular fibrillation or death without prior appropriate ICD therapy. We analyzed cumulative incidence functions and used competing risk regression to study predictors of appropriate ICD therapy or prior death. In 442 patients, 73 deaths occurred during a median follow-up of 3.6 years (maximum, 12.7 years). The cumulative incidence of first appropriate ICD therapy until year 7 was 52%, whereas 11% died without prior ICD therapy. The cumulative incidence of appropriate ICD therapy for ventricular fibrillation was 13%, whereas 23% died without prior therapy for ventricular fibrillation. Appropriate ICD therapy was twice as likely in secondary prevention compared with primary prevention, whereas death rates before ICD therapy were similar in both groups. Diuretic use for heart failure compared with nonuse predicted a 4-fold-increased risk of death prior to ICD therapy, although the incidence of appropriate ICD therapy was similar in both groups. Conclusion— In a contemporary ICD population, the risk of death without prior appropriate ICD therapy is substantial, especially in patients with advanced heart failure.

Cryoballoon versus radiofrequency catheter ablation of paroxysmal atrial fibrillation: Biomarkers of myocardial injury, recurrence rates, and pulmonary vein reconnection patterns

BACKGROUND Cryoballoon ablation has emerged as a novel treatment strategy for patients with atrial fibrillation (AF). OBJECTIVE The purpose of this study was to compare pulmonary vein isolation (PVI) using cryoballoon ablation versus RF ablation with regard to myocardial injury, pulmonary vein (PV) reconnection patterns, and outcome. METHODS Fifty patients (age 59 ± 9 years, ejection fraction 0.59 ± 0.06, left atrial size 41 ± 5 mm) with paroxysmal AF were studied. Twenty-five patients underwent PVI using a 28-mm cryoballoon. A control group of 25 patients underwent PVI using an open-irrigation RF ablation catheter. Myocardial injury was determined by measuring troponin T (TnT). PV reconnection patterns were studied in case of repeat procedures. RESULTS Procedure duration was 166 ± 32 minutes in the cryoballoon group versus 197 ± 52 minutes in the RF group (P = .014), with similar ablation times (cryoballoon: 45 minutes [interquartile range 40-52.5 minutes]; RF: 47 minutes [interquartile range 44-65 minutes], P = .17). Postprocedural TnT in the RF group was 1.29 ± 0.41 μg/L versus 0.76 ± 0.55 μg/L in the cryoballoon group (P = .002). In 12 patients who underwent repeat ablation, 74% of PV reconnection sites were inferiorly located in the cryoballoon group compared to 17% in the RF group (P = .0004). With 1.2 ± 0.4 and 1.3 ± 0.6 procedures per patient, 88% of patients in the cryoballoon group and 92% in the RF group were in stable sinus rhythm after follow-up of 12 ± 3 months (P = NS). CONCLUSION Differences in the extent of myocardial injury and patterns of PV reconnection were observed between cryoballoon ablation and RF ablation of paroxysmal AF.

Competing risks analyses: objectives and approaches.

Studies in cardiology often record the time to multiple disease events such as death, myocardial infarction, or hospitalization. Competing risks methods allow for the analysis of the time to the first observed event and the type of the first event. They are also relevant if the time to a specific event is of primary interest but competing events may preclude its occurrence or greatly alter the chances to observe it. We give a non-technical overview of competing risks concepts for descriptive and regression analyses. For descriptive statistics, the cumulative incidence function is the most important tool. For regression modelling, we introduce regression models for the cumulative incidence function and the cause-specific hazard function, respectively. We stress the importance of choosing statistical methods that are appropriate if competing risks are present. We also clarify the role of competing risks for the analysis of composite endpoints.

Risk for Incident Atrial Fibrillation in Patients Who Receive Antihypertensive Drugs: A Nested Case–Control Study

BACKGROUND Different antihypertensive drug classes may alter risk for atrial fibrillation. Some studies suggest that drugs that interfere with the renin-angiotensin system may be favorable because of their effect on atrial remodeling. OBJECTIVE To assess and compare the relative risk for incident atrial fibrillation among hypertensive patients who receive antihypertensive drugs from different classes. DESIGN Nested case-control analysis. SETTING The United Kingdom-based General Practice Research Database, a well-validated primary care database comprising approximately 5 million patient records. PATIENTS 4661 patients with atrial fibrillation and 18,642 matched control participants from a population of 682,993 patients treated for hypertension. MEASUREMENTS A comparison of the risk for atrial fibrillation among hypertensive users of angiotensin-converting enzyme (ACE) inhibitors, angiotensin II-receptor blockers (ARBs), or beta-blockers with the reference group of users of calcium-channel blockers. Patients with clinical risk factors for atrial fibrillation were excluded. RESULTS Current exclusive long-term therapy with ACE inhibitors (odds ratio [OR], 0.75 [95% CI, 0.65 to 0.87]), ARBs (OR, 0.71 [CI, 0.57 to 0.89]), or beta-blockers (OR, 0.78 [CI, 0.67 to 0.92]) was associated with a lower risk for atrial fibrillation than current exclusive therapy with calcium-channel blockers. LIMITATION Blood pressure changes during treatment courses could not be evaluated, and risk for bias by indication cannot be fully excluded in an observational study. CONCLUSION In hypertensive patients, long-term receipt of ACE inhibitors, ARBs, or beta-blockers reduces the risk for atrial fibrillation compared with receipt of calcium-channel blockers. PRIMARY FUNDING SOURCE None.

The prognosis of implantable defibrillator patients treated with cardiac resynchronization therapy: Comorbidity burden as predictor of mortality

Aims Comorbidity, such as myocardial infarction, diabetes, and renal failure, plays a pivotal role in the prognosis of a patient with arrhythmias. However, data on the prognostic impact of comorbiditiy in heart failure patients with cardiac resynchronization therapy and defibrillation (CRT-D) are scarce. The purpose of this study was to determine the impact of comorbidity on survival in CRT-D patients. Methods and results The study population consisted of 463 heart failure patients who received a CRT-D between 1999 and 2008 in Rotterdam and Basel. The Charlson comorbidity index (CCI) is often used as an adjusting variable in prognostic models. The Cox proportional hazards analysis was performed to determine the independent effect of comorbidity on survival. During a median follow-up of 30.5 months, 85 patients died. Mortality rates at 1 and 7 years were 6.3 and 32.3%. Cumulative incidence of implantable cardioverter defibrillator (ICD) therapy at 7 years was 50%, and death without ICD therapy was observed in 9% of patients. At least three comorbid conditions were observed in 81% of patients. Patients who died had a higher CCI score compared with those who survived (3.9 ± 1.5 vs. 2.9 ± 1.5; P < 0.001). An age-adjusted CCI score ≥5 was a predictor of mortality (hazard ratio 3.69, 95% CI 2.06–6.60; P < 0.001) independent from indication for ICD therapy, and from ICD interventions during the clinical course. Conclusion Comorbidity is often present in heart failure patients, and a high comorbidity burden was a significant predictor of mortality in CRT-D recipients. Comorbidity cannot predict appropriate ICD therapy. Death without prior ICD therapy occurs in a minor proportion of patients.

Initial impedance decrease as an indicator of good catheter contact: Insights from radiofrequency ablation with force sensing catheters

BACKGROUND Good catheter-tissue contact force (CF) is critical for transmural and durable lesion formation during radiofrequency (RF) ablation but is difficult to assess in clinical practice. Tissue heating during RF application results in an impedance decrease at the catheter tip. OBJECTIVE The purpose of this study was to correlate achieved CF and initial impedance decreases during atrial fibrillation (AF) ablation. METHODS We correlated achieved CF and initial impedance decreases in patients undergoing ablation for AF with two novel open-irrigated CF-sensing RF catheters (Biosense Webster SmartTouch, n = 647 RF applications; and Endosense TactiCath, n = 637 RF applications). We then compared those impedance decreases to 691 RF applications with a standard open-irrigated RF catheter (Biosense Webster ThermoCool). RESULTS When RF applications with the CF-sensing catheters were analyzed according to an achieved average CF <5 g, 5-10 g, 10-20 g, and >20 g, the initial impedance decreases during ablation were larger with greater CF. Corresponding median values at 20 seconds were 5 Ω (interquartile range [IQR] 2-7), 8 Ω (4-11), 10 Ω (7-16), and 14 Ω (10-19) with the SmartTouch and n/a, 4 Ω (0-10), 8 Ω (5-12), and 13 Ω (8-18) with the TactiCath (P <.001 between categories for both catheters). When RF applications with the SmartTouch (CF-sensing catheter, median achieved CF 12 g) and ThermoCool (standard catheter) were compared, the initial impedance decrease was significantly greater in the CF-sensing group with median decreases of 10 Ω (6-14 Ω) vs 5 Ω (2-10 Ω) at 20 seconds (P <.001 between catheters). CONCLUSION The initial impedance decrease during RF applications in AF ablations is larger when greater catheter contact is achieved. Monitoring of the initial impedance decrease is a widely available indicator of catheter contact and may help to improve formation of durable ablation lesions.

Longevity of implantable cardioverter-defibrillators, influencing factors, and comparison to industry-projected longevity

BACKGROUND Because the best possible device longevity is crucial (i.e., risk of infection with premature device exchange, current cost-effectiveness calculations depending on reasonable longevity, patient comfort), industry-independent real-life data are fundamental. However, only limited independent data on the longevity of implantable cardioverter-defibrillators (ICDs) are available. OBJECTIVE The purpose of this study was to determine ICD device longevity and influencing factors. METHODS From a prospective database, we studied overall device longevity and identified those devices with replacement for battery depletion or prolonged charge time. For every device, we determined factors that included averaged shocks, pacing percentage, pacing mode, device size, and time of implant. Survival probabilities at different time intervals were calculated, and Kaplan-Meier and Cox regression analyses were used. Observed longevity was compared to industry-projected longevity obtained from product performance reports. RESULTS A total of 644 ICDs (Medtronic 317, Guidant 189, St. Jude 118, Intermedics 20) were implanted in 499 patients. During follow-up, 163 (25.3%) ICDs were replaced. Manufacturer, time of implant, pacing mode, pacing percentage, and capacitor reformation interval influenced longevity, whereas device size and number of shocks did not. Median longevity was 7.6 years for Medtronic devices, 5.0 years for Guidant devices, and 3.8 years for St. Jude devices. After 5 years, only 70% of ICDs were still in service compared to the 80% projected by industry. CONCLUSION Marked differences in device longevity among manufacturers cannot be explained by pacing mode, number of shocks, or pacing percentage only. Overall, device performance requires further improvement for the sake of patient health and cost.

An Electrocardiogram-Based Algorithm To Detect Loss of Left Ventricular Capture during Cardiac Resynchronization Therapy

Context Cardiac resynchronization therapy using biventricular pacing can improve heart failure in selected patients. Worsening heart failure in such patients may be due to failure to pace both ventricles, but this diagnosis is difficult to make without using a programming device. Contribution This study identifies a highly sensitive (93%) and specific (94%) algorithm for using 12-lead electrocardiography to identify loss of left ventricular pacing. Cautions In the study, cardiologists evaluated the electrocardiograms. The algorithm may be less accurate in the hands of noncardiologists. The Editors Left ventricular chamber enlargement and left bundle-branch block in patients with chronic heart failure are often associated with marked dyssynchrony between right and left ventricular contraction (1, 2). The delayed activation and delayed onset of left ventricular free-wall contraction may contribute to hemodynamic deterioration and left ventricular remodeling (3). Cardiac resynchronization therapy can improve quality of life and results in better survival in selected patients with heart failure (4-10). Advances in medical therapy are improving the survival rate among patients with heart failure, and implantation of cardiac resynchronization devices will increase (11). Electrophysiologists, cardiologists, and general practitioners will therefore come to care for a growing number of patients who have cardiac resynchronization devices. Proper biventricular capture is not always easy to confirm without the use of a programming device. We therefore sought to develop and assess a novel and readily applicable algorithm that allows physicians to easily identify loss of left ventricular pacing on the basis of a 12-lead electrocardiogram. Methods Electrocardiographic Analysis The first part of the study included 10 patients with implanted cardiac resynchronization devices. A 12-lead electrocardiogram in the right and biventricular pacing modes was obtained. During biventricular stimulation, the resulting surface electrocardiogram represents a fusion of right and left ventricular pacing. An algorithm to detect loss of left ventricular capture was derived from analysis of the RS spike ratio on the 12-lead electrocardiogram during the different pacing modes (Figure 1). Figure 1. Algorithm to identify biventricular pacing in patients with an implanted cardiac resynchronization device. Two blinded general cardiologists then tested the algorithm. One hundred eight electrocardiograms were obtained from 54 patients with cardiac resynchronization devices, during programmer-confirmed biventricular pacing and after the device was programmed to right ventricular pacing only (to simulate loss of left ventricular capture). All patients had underlying left bundle-branch block before implantation of the cardiac resynchronization device. The 10 patients from the initial study were not included in this cohort. The position of the left ventricular lead was assessed by analysis of lateral and posteroanterior radiographic images, according to methods described elsewhere (12). Assessment of Correct Right and Left Ventricular Pacing Threshold values for left and right ventricular pacing were assessed in the biventricular and right ventricular pacing mode before the electrocardiograms were analyzed. The pacing thresholds (measured in volts) were doubled, and the cardiac resynchronization device was programmed accordingly. One 12-lead electrocardiogram was obtained after the device was programmed into the right ventricular pacing mode, and 1 was obtained with the device in the biventricular pacing mode. In all patients, the right ventricular electrode was placed in the apex of the right ventricle and the left ventricular electrode was placed in the coronary sinus. Statistical Analysis The sensitivity, specificity, positive and negative predictive values, and likelihood ratio that the algorithm would correctly identify loss of biventricular pacing were calculated by using 2-way contingency table analysis software (available at members.aol.com/johnp71/ctab2x2.html) (13). The interobserver agreement was 96.3%. Through discussion, 2 of the investigators reached consensus on the interpretation of the 4 electrocardiograms with discrepant interpretations, so that further statistical analysis could be done. Results Accuracy of the Algorithm The algorithm correctly identified 19 electrocardiograms that showed biventricular capture (35%) on analysis of lead V1 only. In another 31 electrocardiograms (57%) that showed biventricular capture, analysis of lead I as well as lead V1 was needed. The algorithm did not correctly identify biventricular capture in 4 electrocardiograms (8%). Figure 2 shows electrocardiographic traces from leads V1 and I in 1 patient. In the top electrocardiographic tracing, the cardiac resynchronization device is programmed to the right ventricular pacing mode. The other tracings show the continuous shift of the axis in leads V1 and I during resynchronization with left ventricular pacing offsets of 0 ms, 40 ms, and 80 ms. Figure 2. Electrocardiographic tracings from lead V1 and I in 1 patient with an implanted cardiac resynchronization device. top 2nd from top 2nd from bottom bottom The algorithm correctly identified right ventricular pacing in 51 (94%) of 54 patients with simulated loss of biventricular capture (right ventricular pacing only). However, the algorithm correctly identified 50 (93%) of 54 patients with true biventricular capture. Thus, the overall sensitivity to detect loss of biventricular capture was 94% (95% CI, 88.2% to 97.7%), and the specificity was 93% (CI, 86.3% to 95.8%). The positive and negative predictive values were 93% (CI, 86.6% to 95.9%) and 94% (CI, 87.9% to 97.6%), respectively. The likelihood ratio of a positive test result was 12.8 (CI, 6.443 to 23.310), and the likelihood ratio of a negative test result was 0.06 (CI, 0.024 to 0.137). Role of the Position of the Coronary Sinus Lead Coronary sinus leads were placed in the posterior and left marginal veins in 41 (76%) patients, the anterior cardiac vein (diagonal branches) in 10 (19%) patients, and the middle cardiac vein in 3 (5%) patients. All right ventricular pacing leads were placed in an apical right ventricular position. The algorithm correctly identified biventricular pacing in 100% of patients with leads placed in the diagonal branches of the anterior interventricular vein, 100% of those with leads in the middle cardiac vein, and 90% of those with leads in the posterior and left marginal veins. Figure 3 shows correct identification of biventricular pacing in a patient with a coronary sinus lead in the left marginal vein (part A) and the same patient with right ventricular pacing only (part B). Figure 3. Coronary sinus electrode placement in the lateral cardiac vein ( A and B ) and the posterior cardiac vein ( C and D ) of 2 different patients with an implanted cardiac resynchronization device. A. B. C. D. Discussion We devised an algorithm that reliably detects loss of left ventricular capture in patients with a cardiac resynchronization device and left bundle-branch block. The sensitivity and specificity of the algorithm are high (94% [CI, 88.2% to 97.7%] and 93% [CI, 86.3% to 95.8], respectively). The algorithm is based on local electrograms obtained from lead V1 (the only chest lead overlying the right ventricle) and lead I. When the left ventricle is activated, the main electrical vector is directed toward lead V1. Because there is always fusion with the concurrent right ventricular apical stimulation, a complete right bundle-branch block pattern in lead V1 is very rare. However, we found that an RS spike ratio of 1 or greater can reliably detect left ventricular capture. Lead I needs to be assessed only if fusion with right ventricular stimulation is causing a mainly negative deflection in lead V1. In this case, left ventricular stimulation will cause a negative deflection because the main vector is now directed from the left to the right side, pointing away from lead I (Figure 4). Figure 4. Main QRS axis during biventricular pacing, relative to electrocardiograph leads I and V1. Few data are available on use of the 12-lead surface electrocardiogram to detect left ventricular capture in patients with a cardiac resynchronization device. Ricci and colleagues (14) studied the relationship between QRS morphology and lead site in 48 patients. They found that the QRS axis during biventricular pacing was poorly related to positioning of the left ventricular lead and did not allow discrimination between anterior and posterolateral positioning. The QRS axes for lateral, anterior, inferior, and posterior lead position in biventricular pacing were 129 68, 64 46, 93 23, and 62 37, respectively. These investigators did not provide an algorithm to identify left ventricular capture on the basis of a 12-lead electrocardiogram. Convincing evidence indicates that cardiac resynchronization therapy is beneficial in patients with heart failure and left bundle-branch block (5-9). Some reports also indicate that resynchronization therapy may also benefit patients with right bundle-branch block, under certain circumstances (15, 16). Our algorithm was tested in patients with left bundle-branch block only and should therefore be used solely in these patients. The algorithm correctly identified biventricular pacing in 100% of patients with coronary sinus leads in the diagonal branches of the anterior cardiac vein, 100% of those with leads in the middle cardiac vein, and 90% of those with leads in the posterior and left marginal veins. Because the target site for placement of left ventricular leads is usually the vein in which electrical left ventricular activation is most delayed (most often the posterior and left marginal veins), our algorithm will help to identify correct biventricular pacing in at least 90% of patients with cardiac resynchronization devices (12). O

Validation of a novel spiral mapping catheter for real-time recordings from the pulmonary veins during cryoballoon ablation of atrial fibrillation

BACKGROUND The Achieve mapping catheter allows real-time recordings from the pulmonary veins (PVs) during cryoballoon (CB) ablation of atrial fibrillation (AF). OBJECTIVE To assess the clinical applicability of the Achieve mapping catheter and the value of real-time recordings from the PVs during CB. METHODS Patients with paroxysmal AF undergoing CB ablation were studied. Recordings from the PVs were analyzed during (real-time recordings) and after CB ablation and validated by using a variable circumferential mapping catheter (Achieve group; n = 20). A comparison was made by using a group of patients in whom CB ablation with a guidewire and a variable circumferential mapping catheter was performed (Guidewire group; n = 20). RESULTS Forty patients (age 58±11 years; ejection fraction 0.59±0.07; left atrial size 40±6 mm) with paroxysmal AF were included. In the Achieve group, real-time recordings from the PVs could be obtained in 40 of 80 (50%) PVs and could be seen more often at the left-sided PVs (25 of 39, 64%) than at the right-sided PVs (15 of 41, 37%; P = .02). Validation with a standard circumferential mapping catheter confirmed PV isolation in 75 of 80 (93%) PVs. After a single procedure and a follow-up of 14±4 months, 25 of 40 (63%) patients were in sinus rhythm with no significant difference between groups. CONCLUSIONS The Achieve catheter can be used as a substitute for a guidewire during CB ablation, but real-time recordings can be obtained only in half of the PVs and are not sufficient to accurately confirm isolation of all PVs.