Echocardiographic transponder-guided catheter ablation feasibility and accuracy.

BACKGROUND: The utility of echocardiography for catheter guidance during percutaneous endocardial ablation is increasingly apparent. However, the technique is currently imperfect due to limitations in discerning the ablation electrode from other parts of the catheter shaft. PURPOSE: To examine the feasibility and accuracy of echocardiography-guided ablation using commercial ablation catheters fitted with a transponder to improve localization of the ablation electrode. METHODS: Fifteen healthy pigs and five pigs with chronic anterior myocardial infarction were studied. In healthy animals, echocardiographically distinct endocardial sites in right and left cardiac chambers were targeted for ablation. In infarcted animals, the left ventricular infarction border zone was targeted. Both intracardiac (ICE; 12.5 megahertz and 5 megahertz) and transesophageal echocardiographic (TEE) techniques were utilized. RESULTS: In healthy animals, transponder-guided ablation was feasible with each of the echocardiographic techniques. Accuracy was 82 % (45 of 55 lesions) with ICE-12.5 MHz, 87 % (27 of 31 lesions) with ICE-5 MHz, and 81 % (22 of 27 lesions) with TEE. In infarcted animals, the accuracy was 38 % (3 of 8 lesions) for ICE-5 MHz and 38 % (3 of 8 lesions) for TEE. Errant lesions in healthy animals were observed in earlier experiments, due to operator misinterpretation of the plane of imaging. Errant lesions in infarcted animals were observed throughout the experimental series, and may have been due to a variable relationship between echocardiographic and histologic infarction border zones. CONCLUSIONS: Echocardiographic transponder-guided catheter ablation is feasible. Accuracy for normal endocardial targets was excellent, less so for chronic infarction border.

Reversal of tachycardia induced cardiomyopathy following ablation of repetitive monomorphic right ventricular outflow tract tachycardia.

Radiofrequency catheter ablation was performed in four adults with myocardial dysfunction related to repetitive monomorphic ventricular tachycardia (RMVT) originating in the right ventricular outflow tract. Serial echocardiographic assessment of left ventricular function before and after radiofrequency catheter ablation of RMVT showed complete reversal of left ventricular dysfunction without arrhythmia recurrence during 31+/-28 months follow-up.

Prognostic value of heart rate variability analysis in patients with carcinoid syndrome.

BACKGROUND/AIMS: Recently, a decrease in heart rate variability measures was found in patients with carcinoid syndrome suffering from carcinoid heart disease compared to those without cardiac involvement of carcinoid syndrome. The prognostic relevance of this finding, however, was not clear. PATIENTS AND METHODS: Therefore, 35 patients with carcinoid syndrome (21 men, age 56 +/- 11 years), all of them suffering from metastatic carcinoid tumors, were followed prospectively at our institution. Digital 24-hour Holter monitoring, echocardiography, and serum serotonin and urine 5-hydroxyindole acetic acid (5-HIAA) samplings were performed in all study patients at baseline. Indices of time domain heart rate variability obtained from Holter recordings included the standard deviation of all normal RR intervals (SDNN) representing overall variability, the square root of the mean of the squared differences between adjacent normal RR intervals (rMSSD), and the percentage of the number of pairs of adjacent normal RR intervals differing by >50 ms (pNN50), both indices reflecting predominantly vagal influences on heart rate. RESULTS: During a mean follow-up of 18 +/- 7 months, 15 of 35 patients with carcinoid syndrome (43%) died. Patients with cardiac manifestation of the carcinoid syndrome showed a tendency towards an increased mortality in comparison to patients without cardiac involvement (p = 0.09). Patients with the combination of decreased heart rate variability (SDNN <100 ms) and presence of carcinoid heart disease had a significant worse prognosis (p = 0.04) compared to patients without carcinoid heart disease and preserved heart rate variability (SDNN > or =100 ms). CONCLUSIONS: The presence of carcinoid heart disease in combination with decreased heart rate variability is associated with the most adverse prognosis in the setting of carcinoid syndrome.

Outcome of patients with sleep apnea-associated severe bradyarrhythmias after continuous positive airway pressure therapy.

Twenty-nine patients in whom severe bradyarrhythmias occurred exclusively during obstructive sleep apnea and in whom advanced sinus node disease or atrioventricular conduction system dysfunction had been excluded by invasive electrophysiologic evaluation were prospectively followed on nasal continuous positive airway pressure. During 54 +/- 10 months follow-up, no syncope and no sudden deaths were observed, suggesting that patients with sleep apnea-associated bradyarrhythmias and a normal electrophysiologic study appear to have a favorable prognosis with continuous positive airway pressure.

Prediction of major arrhythmic events and sudden cardiac death in dilated cardiomyopathy. The Marburg Cardiomyopathy Study design and description of baseline clinical characteristics.

The Marburg Cardiomyopathy Study (MACAS) is a prospective observational study designed to determine the value of the following potential non-invasive arrhythmia risk predictors in more than 200 patients with idiopathic dilated cardiomyopathy (IDC) over a 5-year follow-up period: New York Heart Association functional class, left ventricular end-diastolic diameter and ejection fraction, left bundle branch block and atrial fibrillation on ECG, QTc and JTc-dispersion on 12-lead ECG, abnormal time-domain analysis and spectral turbulence analysis of the signal-averaged ECG, ventricular arrhythmias and heart-rate variability on 24-hour Holter ECG, baroreflex sensitivity, and microvolt T wave alternans during exercise. This report describes the rationale of MACAS as well as the clinical characteristics of the first 236 patients enrolled between March 1996 and October 1999. The prognostic significance of the potential arrhythmia risk predictors in MACAS will be determined by multivariate Cox analysis at the end of 5-year follow-up. Primary endpoints are total mortality and major arrhythmic events defined as sustained ventricular tachycardia, ventricular fibrillation or sudden cardiac death. The results of MACAS will have important implications for the design of future studies evaluating the role of prophylactic defibrillator therapy in idiopathic dilated cardiomyopathy.

Arrhythmia risk stratification in idiopathic dilated cardiomyopathy based on echocardiography and 12-lead, signal-averaged, and 24-hour holter electrocardiography.

BACKGROUND: To date, considerable controversy exists regarding noninvasive arrhythmia risk stratification in idiopathic dilated cardiomyopathy (IDC). Methods and Results Between 1992 and 1997, 202 patients with IDC without a history of sustained ventricular tachycardia (VT) underwent echocardiography, signal-averaged electrocardiogram (ECG), and 24-hour Holter ECG in the absence of antiarrhythmic drugs. During 32 +/- 15 months of prospective follow-up, major arrhythmic events, including sustained VT, ventricular fibrillation, or sudden death, occurred in 32 (16%) of 202 patients. After adjusting for baseline medical therapy and antiarrhythmic therapy during follow-up, multivariate Cox regression analysis identified a left ventricular (LV) end-diastolic diameter >/=70 mm and nonsustained VT on Holter as the only independent arrhythmia risk predictors. The combination of an LV end-diastolic diameter >/=70 mm and nonsustained VT was associated with a 14. 3-fold risk for future arrhythmic events (95% confidence interval 2. 3-90). To further elucidate the prognostic value of LV ejection fraction, multivariate Cox analysis was repeated with ejection fraction forced to remain in the model. In the latter model, an ejection fraction /=70 mm and nonsustained VT on Holter, and the combination of LV ejection fraction

Restenosis after percutaneous coronary interventions and infection.

Infectious agents may directly or indirectly (through the response of the host's immune system) modulate the growth of vascular cells. Local and/or systemic increase of cytokines could influence the extent of (re-)stenosis in the vascular tree. Further studies in this field may identify patients at a high risk for atherogenesis and restenosis. Their results should be helpful in treating restenosis after percutaneous coronary interventions.

Significance of accelerated idioventricular rhythm in idiopathic dilated cardiomyopathy.

Holter monitoring was performed in 202 patients with idiopathic dilated cardiomyopathy, which revealed accelerated idioventricular rhythm in 16 patients (8%) and nonsustained ventricular tachycardia in 70 patients (35%). During 32 +/- 15-month prospective follow-up, no significant difference was observed for major arrhythmic events and transplant-free survival between patients with and without accelerated idioventricular rhythm, whereas patients with nonsustained ventricular tachycardia had a significantly higher incidence of major arrhythmic events and a lower transplant-free survival rate.

Heart rate variability and baroreflex sensitivity in idiopathic dilated cardiomyopathy.

OBJECTIVE: To examine the relation between cardiac autonomic tone, assessed by baroreflex sensitivity and heart rate variability, and left ventricular function, arrhythmias on Holter monitoring, and clinical variables in patients with idiopathic dilated cardiomyopathy. DESIGN: A prospective observational study. PATIENTS: 160 patients with idiopathic dilated cardiomyopathy and preserved sinus rhythm in the absence of antiarrhythmic drug treatment. Measures of heart rate variability obtained by digital 24 hour Holter recordings included the mean of all coupling intervals between normal beats (RRm), the standard deviation of the mean of normal RR intervals (SDNN), and the square root of the mean of the squared differences between adjacent normal RR intervals (rMSSD). Baroreflex sensitivity testing was performed using the phenylephrine method. RESULTS: Mean SDNN (SEM) was 112 (46) ms, and baroreflex sensitivity was 7.5 (5.0) ms/mm Hg. SDNN showed a weak correlation with baroreflex sensitivity (r = 0.19, p < 0.05) and with left ventricular ejection fraction (r = 0.29, p < 0.05). SDNN showed no significant correlation with age (r = -0.07), the presence of non-sustained ventricular tachycardia (r = -0.13), or left ventricular end diastolic diameter (r = -0.07). In addition, baroreflex sensitivity showed no significant correlation with age (r = -0.13), non-sustained ventricular tachycardia (r = -0.08), left ventricular end diastolic diameter (r = 0.09), or ejection fraction (r = 0.14). CONCLUSIONS: The weak correlation between baroreflex sensitivity and heart rate variability suggests that these two indices explore different aspects of cardiac autonomic control in patients with idiopathic dilated cardiomyopathy. The weak or absent correlation between baroreflex sensitivity, heart rate variability, and other potential non-invasive risk predictors, including left ventricular ejection fraction, left ventricular end diastolic diameter, and non-sustained ventricular tachycardia on Holter monitoring, indicate that these variables may have independent prognostic value in idiopathic dilated cardiomyopathy.

[Correlation between cardiac autonomic activity and compromise of left ventricular function in dilated cardiomyopathy]. / Zusammenhang zwischen kardialer autonomer Aktivität und linksventrikulärer Funktionseinschränkung bei dilatativer Kardiomyopathie.

In recent years, evaluation of cardiac autonomic activity by means of heart rate variability (HRV) determination and baroreflex sensitivity (BRS) testing has become readily available. The results of the ATRAMI (Autonomic Tone and Reflexes After Myocardial Infarction) study showed that both diminished HRV and baro-reflex sensitivity are associated with poor outcome in patients after myocardial infarction. In contrast to patients with coronary disease little information is available concerning cardiac autonomic activity in idiopathic dilated cardiomyopathy (IDC). Therefore, HRV and BRS were assessed in 160 patients with IDC and preserved sinus rhythm in order to investigate the relationship between HRV, BRS, and left ventricular ejection fraction. Time domain indices of HRV were computed from 24-hour digital Holter recordings. BRS testing was performed using the noninvasive phenylephrine method. Mean standard deviation of all normal RR intervals (SDNN) of the whole study population was 112 +/- 46 ms. A well preserved HRV (SDNN > 105 ms) was found in 74 patients (46%), a moderately decreased HRV (SDNN 70-105 ms) in 59 patients (37%), and a severely decreased HRV (SDNN < 70 ms) in 27 patients (17%). Mean BRS was 7.5 +/- 5.0 ms/mm Hg. A well preserved BRS (> 6 ms/mm Hg) was present in 78 patients (57%), a moderately decreased BRS (3-6 ms/mm Hg) was present in 38 patients (28%), and a severely decreased BRS (< 3 ms/mm Hg) in 21 patients (15%). There was only a weak correlation between SDNN and BRS (r = 0.19; p < 0.05). A weak correlation was found for SDNN and left ventricular ejection fraction (r = 0.29; p < 0.05). There was no significant correlation between BRS and left ventricular ejection fraction (r = 0.14). In summary, there was only a weak correlation between the HRV, BRS, and left ventricular ejection fraction in patients with IDC suggesting that these 3 variables may be independent predictors of sudden death in IDC. The relative prognostic value of these variables and other potential risk predictors including the presence of arrhythmias on Holter, microvolt T wave alternans, QTc dispersion, and signal-averaged ECG is currently under investigation in a large prospective observational study (Marburg Cardiomyopathy Study (MACAS)) during 5-year follow-up at our institution.

Cardiac autonomic tone and its relation to nonsustained ventricular tachyarrhythmias in idiopathic dilated cardiomyopathy.

BACKGROUND: In contrast to postinfarct patients, little is known about cardiac autonomic tone and its relation to spontaneous ventricular tachyarrhythmias in idiopathic dilated cardiomyopathy (IDC). Both heart rate variability (HRV) and baroreflex sensitivity (BRS) are indices of autonomic innervation of the heart. HYPOTHESIS: The aim of the present study was to determine the relation between cardiac autonomic tone assessed by HRV and BRS and spontaneous nonsustained ventricular tachycardia (NSVT) on Holter in a large patient population with IDC. METHODS: 24-h digital Holter recordings including HRV analysis and BRS testing were prospectively performed in 137 patients with IDC and preserved sinus rhythm. Mean age was 48 +/- 12 years, and mean left ventricular (LV) ejection fraction was 32 +/- 9%. The HRV analysis on Holter included the mean RR interval (RRm), the standard deviation of all normal RR intervals (SDNN), the square root of the mean of the squared differences between adjacent normal RR intervals (rMSSD), and the proportion of adjacent normal RR intervals differing more than 50 ms (pNN50). Testing for BRS was performed noninvasively using the phenylephrine method. RESULTS: Of 137 study patients, 42 (31%) had spontaneous NSVT on 24-h Holter. Compared with patients without NSVT, patients with NSVT on Holter had a higher New York Heart Association (NYHA) functional class (NYHA III: 40 vs. 18%, p < 0.01), a lower ejection fraction (29 +/- 9 vs. 34 +/- 9%, p = 0.01), and an increased LV end-diastolic diameter (69 +/- 8 mm vs. 66 +/- 7 mm, p = 0.03). The HRV variables rMSSD, pNN50, RRm, and BRS did not differ significantly between patients with and without spontaneous NSVT. Only SDNN on Holter was slightly lower in patients with versus without NSVT (106 +/- 45 vs. 121 +/- 46 ms, p = 0.08). CONCLUSIONS: Patients with IDC and spontaneous NSVT on Holter are characterized by a higher NYHA functional class, a lower LV ejection fraction, an increased LV end-diastolic diameter, and a tendency toward a lower SDNN value compared with patients without NSVT. The remaining measures of HRV including rMSSD and pNN50 reflecting primarily tonic vagal activity, as well as BRS reflecting predominantly reflex vagal activity, were similar in patients with and without NSVT. The prognostic significance of these findings in patients with IDC is currently under investigation in the Marburg Cardiomyopathy Study (MACAS) at our institution.

Prevention of recurrent ventricular fibrillation by ventricular rate stabilization.

This report describes a post-infarct patient with recurrent ventricular fibrillation in the absence of acute ischaemia, in whom arrhythmia recurrences could be prevented by ventricular rate stabilization of a third-generation cardioverter defibrillator. Review of the literature and clinical implications are discussed.

Linear lesion formation by ND:YAG laser versus radiofrequency energy in porcine atria.

The efficacy of RF energy versus the neodymium:yittrium aluminum-garnet laser to create linear lesions was compared in fresh ex vivo swine hearts. A total of 598 lesions were created in four locations: ostium of the pulmonary veins, trabeculated lateral left atrium, smooth posterior part of the right atrium, and the isthmus between the inferior vena cava and tricuspid valve. A 400-micron bare quartz fiber with CO2 cooling (distance to the tissue 5, 10, and 15 mm) and an RF ablation catheter (4-mm tip) were mechanically dragged over the tissue at speeds 0.5, 1.0, and 1.5 mm/s. A continuous and transmural ablation line was recorded as successful. A 100% success rate was achieved at the pulmonary veins and the isthmus at some settings of energy delivery by the laser and RF. In the thick posterior right atrium, RF resulted in transmural lesions only when associated with carbonization, while the laser produced successful ablation lines in 100% of the attempts. In the left atrium, because of the presence of prominent trabeculations, RF was unsuccessful at all settings of energy delivery. In contrast, deep photocoagulation by laser resulted in successful ablations in the left atrium in 100% of attempts. Lesion formation was faster by laser ablation and mean lesion width was at least 25% smaller with the laser than with RF. In conclusion, the formation of linear lesions at the isthmus and at the pulmonary veins was successful with the laser and RF. In the trabeculated left atrium and the thick posterior right atrium, only laser ablation was successful.

Circadian variation and onset mechanisms of ventricular tachyarrhythmias in patients with coronary disease versus idiopathic dilated cardiomyopathy.

To determine the circadian variations and the onset mechanisms of ventricular tachyarrhythmias (VT) in patients with implantable cardioverter defibrillators, stored electrograms of 364 VT episodes occurring in 40 patients with coronary artery disease (CAD) and in 29 patients with idiopathic dilated cardiomyopathy (DCM) were analyzed. A similar circadian distribution of VT episodes was observed in both groups, with a morning peak and less pronounced evening peak. After exclusion of patients with atrial fibrillation, VT onset was classified as (1) sudden if preceded by > or = 8 regular cycles without ventricular premature beats, (2) onset with a short-long-short interval, and (3) a more complex onset with variable patterns of ventricular premature beats before initiation of VT. Sudden onset was found in 26% and 21% of VTs in CAD and DCM respectively. A short-long-short interval preceded 29% of VTs in CAD compared to 14% of VTs in DCM (P < 0.05). A more complex onset was observed in the remaining 45% of VTs in CAD and 65% of VTs in DCM (P < 0.05). In conclusion, patients with DCM and CAD had similar circadian distributions of VT episodes. The majority of episodes were preceded by complex occurrence of ventricular premature beats rather than by the classic short-long-short sequence. These findings have important implications for the development of preventive pacing methods.

Relation between microvolt level T wave alternans and other potential noninvasive predictors of arrhythmic risk in the Marburg Cardiomyopathy Study.

The relation between microvolt level T wave alternans (TWA) and other noninvasive arrhythmia risk predictors was analyzed in 221 consecutive patients with idiopathic dilated cardiomyopathy (IDC) and sinus rhythm enrolled in the Marburg Cardiomyopathy Study between March 1996 and May 2000. TWA analysis was also performed in 110 healthy controls of similar age and sex. TWA during symptom-limited exercise was positive, negative and indeterminate in, respectively, 108 (49%), 65 (29%) and 48 (22%) patients with IDC versus, respectively, 5 (5%), 98 (89%) and 7 (6%) healthy controls (P < 0.05). Patients with IDC and positive TWA had a lower left ventricular (LV) ejection fraction (29 +/- 9% vs 34 +/- 10%, P < 0.05) and greater LV end-diastolic diameter (69 +/- 8 mm versus 64 +/- 6 mm, P < 0.05) than patients with negative TWA. Other variables, including age, gender, New York Heart Association functional class, presence of bundle branch block, arrhythmias on 24-hour ambulatory electrocardiogram, heart rate variability and baroreflex sensitivity, were not significantly different between patients with positive vs negative TWA. The prognostic significance of TWA in IDC with regard to arrhythmic events and total mortality will be determined by multivariate Cox analysis at the end of a 5-year follow-up in this ongoing study.

[Prospective evaluation of effect of carvedilol therapy on heart rate variability in patients with dilated cardiomyopathy]. / Einfluss von Carvedilol auf die Herzfrequenzvariabilität bei Patienten mit dilatativer Kardiomyopathie.

The aim of the present study was to assess the effects of carvedilol therapy in addition to conventional heart failure therapy on heart rate variability (HRV) and on left ventricular function in 14 patients with mild to moderate heart failure due to idiopathic dilated cardiomyopathy (IDC). After a 3- to 4-week titration period, carvedilol was titrated up to 50mg daily, or the highest dose tolerated (at least 25mg daily). Maintenance treatment was then continued for 8 weeks. Digital 24-hour Holter recordings were obtained at baseline and after 8 weeks of carvedilol therapy. HRV for the entire 24-hour period was computed in the time domain using the Oxford Medilog Excel 2 analysis system. Measures of HRV included the mean of all coupling intervals between normal beats (RRm), the standard deviation of all normal RR intervals (SDNN), the square root of the mean of the squared differences between adjacent normal RR intervals (rMSSD), and the proportion of adjacent normal RR intervals differing >50 ms (pNN50). Additional treatment with carvedilol induced a significant increase in HRV: SDNN increased from 77+/-21 ms to 110+/-22 ms (p=0.001), rMSSD from 19+/-7 ms to 26+/-7 ms (p=0.02), and mean pNN50-value increased from 1.7+/-1.3% to 5.5+/-4.5% (p<0.01) under therapy with carvedilol. Mean heart rate on carvedilol calculated over 24 hours was 13 beats less than at baseline (75 bpm versus 88 bpm, p<0.01). After 2 months of additional treatment with carvedilol, both hemodynamic and clinical parameters improved: left ventricular ejection fraction increased from 24+/-7% to 30+/-10% (p<0.05), and New York Heart Association class decreased from 2.5+/-0.8 to 1.8+/-0.7 (p<0.05). In summary, eight weeks of additional carvedilol therapy induced a significant increase in HRV parameters related to parasympathetic activity in patients with IDC. Whether increased vagal tone may contribute to the protective effect of carvedilol has to be evaluated by further studies.

Heart rate variability in carcinoid heart disease.

Time domain heart rate variability measurements and echocardiographic studies were performed in 35 patients with carcinoid syndrome. Carcinoid heart disease was present in 18 patients (51%). Heart rate variability parameters (standard deviation of all normal RR intervals, percentage of the number of pairs of adjacent normal RR intervals differing by >50 ms) were significantly reduced in patients with than in those without carcinoid heart disease.

Complications of third-generation implantable cardioverter defibrillator therapy.

To determine the incidence of complications of third-generation implantable cardioverter defibrillator (ICD) therapy, 144 patients were prospectively studied who underwent first implant of third-generation devices (i.e., ICD systems with biphasic shocks, ECG storage capability, and nonthoracotomy lead systems). During 21 +/- 15 months of follow-up, 41 (28%) patients had one or more complications. No patient died perioperatively (30 days) and no ICD infection was observed during follow-up. Complications included bleeding or pocket hematoma (hemoglobin drop > 2 g/dL) in 5 (3%) patients, prolonged reversible ischemic neurological deficit in 1 (1%) patient, postoperative deep venous thrombosis of leg in 1 (1%) patient, pneumothorax in 2 (1%) patients, difficulty to defibrillate ventricular fibrillation intraoperatively in 2 (1%) patients, generator malfunction in 1 (1%) patient, arthritis of the shoulder in 3 (2%) patients, and allergic reaction to prophylactic antibiotics in 2 (1%) patients. A total of seven lead related complications were observed in six (4%) patients including endocardial lead migration in four (3%) patients. Twenty-three (16%) patients received inappropriate shocks for supraventricular tachyarrhythmias (n = 13), non-sustained ventricular tachycardia (VT) (n = 7), or myopotential oversensing (n = 3). We conclude that serious complications such as perioperative death or ICD infection are rare in patients with third-generation ICDs. Lead-related problems and inappropriate shocks during follow-up are the most frequent complications of third-generation ICD therapy. Recognition of these complications should promote advances in ICD technology and management strategies to avoid their recurrence.

Transient QT prolongation with torsades de pointes tachycardia after ablation of permanent junctional reciprocating tachycardia.

INTRODUCTION: Catheter ablation with radiofrequency energy is a curative therapy in patients with permanent junctional reciprocating tachycardia (PJRT). METHODS AND RESULTS: For the first time, we report a case of transient QT prolongation with torsades de pointes tachycardia 18 hours after successful radiofrequency energy ablation of PJRT in a 25-year-old woman with tachycardia-induced cardiomyopathy. Of note, the torsades de pointes occurred in the absence of bradycardia, electrolyte disturbances, or QT-prolonging drugs. This patient initially was thought to have a hereditary long QT syndrome that was unmasked by PJRT ablation. Therefore, the patient received an implantable defibrillator in addition to beta-blocker therapy, which was discontinued 6 months later. Surprisingly, the QT interval completely normalized within 1 week after PJRT ablation, and the patient remained free of arrhythmias during a follow-up period of 4.5 years. CONCLUSION: Patients with incessant tachyarrhythmias should undergo ECG monitoring for at least 24 hours following successful radiofrequency catheter ablation because transient QT prolongation with torsades de pointes may occur even in the absence of bradycardia, QT-prolonging drugs, or electrolyte disturbances.

Recording of pacing stimulus artifacts by endovascular defibrillation lead systems: comparison of true and integrated bipolar circuits.

BACKGROUND: The occurrence ICD undersensing of ventricular fibrillation due to the presence of a pacing stimulus artifact (PSA) is in part related to the amplitude of the artifact recorded on the ICD rate sensing circuit. There is little comparative data regarding PSA amplitude recorded by commercial ICD rate-sensing circuits. PURPOSE: To compare PSA amplitude recorded by commercial endovascular defibrillation leads utilizing integrated or true bipolar sensing circuits. METHODS: Nineteen large (60-120 kg) pigs were utilized. Two different commercial endovascular defibrillation leads were evaluated, each with its distal tip located at the right ventricular apex: (1) Medtronic Transvene; and (2) CPI Endotak. Three different rate-sensing circuits were evaluated: (1) Transvene true bipolar (tip-ring); (2) Transvene integrated bipolar (tip-coil); and (3) Endotak integrated bipolar (tip-coil). Using a separate pacing lead located at the left ventricular apex (n = 19 animals) or right ventricular outflow tract (n = 10 animals), pacing was performed at a pulse width of 0.5 milliseconds at outputs of 1.5, 5 and 10 volts. PSA amplitude was recorded at each output by each circuit. RESULTS: During pacing from the left ventricular apex, at each pacing output voltage the PSA amplitude recorded by the true bipolar circuit (0.6 +/- 0.1 mV at 1.5 volts, 2.0 +/- 0.5 mV at 5 volts, 3.7 +/- 0.8 mV at 10 volts) was significantly smaller than recorded by the Transvene integrated circuit (1.4 +/- 0.3 mV at 1.5 volts, 3.8 +/- 0.7 mV at 5 volts, 4.1 +/- 0.8 mV at 10 volts) or the Endotak integrated circuit (1.8 +/- 0.4 mV at 1.5 volts, 4.2 +/- 1.0 mV at 5 volts, 6.3 +/- 1.8 mV at 10 volts). During pacing from the right ventricular outflow tract, at each pacing output voltage the PSA amplitude recorded by the true bipolar circuit (0.7 +/- 0.1 mV at 1.5 volts, 1.7 +/- 0.4 mV at 5 volts, 4.0 +/- 0.7 mV at 10 volts) was significantly smaller than recorded by the Transvene integrated circuit (1.1 +/- 0.4 mV at 1.5 volts, 3.9 +/- 1.2 mV at 5 volts, 7.5 +/- 1.8 mV at 10 volts) or the Endotak integrated circuit (1.6 +/- 0.7 mV at 1.5 volts, 4.3 +/- 1.7 mV at 5 volts, 7.5 +/- 2.6 mV at 10 volts). For both pacing sites, the PSA amplitude recorded by the two integrated circuits was not significantly different. CONCLUSIONS: For a given pacing output voltage, PSA amplitude recorded by commercial endovascular rate sensing/defibrillation leads is greater when the sensing circuit is integrated than when it is true bipolar. These data may be helpful in planning ICD implantation in patients with previously implanted permanent pacemakers.