The benefit of upgrading chronically right ventricle-paced heart failure patients to resynchronization therapy demonstrated by strain rate imaging.

BACKGROUND: RV pacing induces conduction delay (CD), mechanical dyssynchrony, and increased morbidity in patients with HF. CRT improves HF symptoms and survival, but sparse data exist on its direct effect on chronically RV-paced HF patients. OBJECTIVES: To assess the benefit of cardiac resynchronization therapy (CRT) in chronically right ventricle (RV)-paced heart failure (HF) patients. METHODS: We studied 12 consecutive patients with class III HF who had a previously implanted pacemaker or implantable cardioverter-defibrillator. These individuals were chronically RV paced and referred for upgrade to a biventricular device by their primary cardiologists. Tissue Doppler and strain rate imaging (TDI and SRI, respectively) were performed immediately before each upgrade and 4-6 weeks afterward to quantify changes in regional wall motion and synchrony with CRT. RESULTS: CRT significantly reduced the mean QRS duration (205 ms to 156 ms; P<.0001), and it increased the ejection fraction (30.7%+/-5.1% to 35.8%+/-5.1%; P<.01). Left ventricular end-systolic and end-diastolic dimensions were also significantly reduced. Clinically, patients improved by an average of one New York Heart Association (NYHA) functional class after upgrade (P = .006). The parameter exhibiting greatest improvement was the coefficient of variation (CoV: standard deviation/mean) of time to peak systolic strain rate, a marker of ventricular dyssynchrony, which decreased from 34.3%+/-13.0% to 19.0%+/-6.6% (P<.01). Reduction in CoV of time to peak systolic strain rate was maximally seen in the midventricle (38.2%+/-19.6% to 16.5%+/-9.7%; P<.01). CONCLUSIONS: Upgrading chronically RV-paced HF patients to CRT improves global and regional systolic function. TDI and SRI provide compelling evidence that this benefit parallels that seen in HF patients with CD unrelated to RV pacing, which implies that biventricular pacing synchronizes mechanical activation in different myocardial regions in patients upgraded from RV pacing as well.

Internal defibrillation with minimal skeletal muscle activation: a new paradigm toward painless defibrillation.

BACKGROUND: Shock-induced pain produces substantial morbidity in recipients of implantable cardioverter-defibrillators (ICDs). This pain likely derives from activation of skeletal muscle and associated nerves in the chest and abdomen. In an effort to develop a painless defibrillation system, we designed an electrode arrangement that incorporates a conductive sock placed around the heart to confine the electric shock field to cardiac tissue. OBJECTIVES: The purpose of this study was to test whether cardiac defibrillation could be achieved without skeletal muscle activation using a novel electrode system. METHODS: Eight adult mongrel dogs were studied. Force of skeletal muscle contraction was measured by strain gauges attached to the forelimbs during delivery of internal shocks ranging in energy from 0.1 to 31 J. Biphasic shocks were delivered (1) between a right ventricular coil and a subcutaneous dummy can (standard configuration), and (2) between a left ventricular coil and an epicardial electrode sock. Internal and external defibrillation thresholds (DFTs) were determined for each electrode configuration. RESULTS: Shock-induced muscle contraction force was significantly lower using the sock electrode than with standard ICD electrodes at every shock energy level tested (P < .0001). Internal DFT was similar between electrode configurations (sock electrode: 8.6 +/- 4.2 J; standard: 11.0 +/- 6.3 J, P = .4), but muscle contraction force at DFT was greatly reduced with the new electrode system (1.8 +/- 2.0 kg vs 10.6 +/- 2.1 kg, P < .0001). The sock electrode rendered external defibrillation impossible, however, even at 360 J. CONCLUSION: Skeletal muscle activation induced by ICD shocks can be greatly reduced using an electrode system that confines the electric shock field to the heart. Refinement of this strategy may allow for delivery of painless shocks by ICDs. Further development is needed to overcome implant complexity and the higher external DFT with this type of electrode system.

Clinical prediction of cavotricuspid isthmus dependence in patients referred for catheter ablation of "typical" atrial flutter.

INTRODUCTION: Typical atrial flutter (AFL) can be cured by catheter ablation of the cavotricuspid isthmus (CTI). The surface electrocardiogram (ECG) is not always diagnostic of isthmus dependence of AFL. The aim of this study was to evaluate clinical parameters for the prediction of isthmus-dependent AFL. METHODS AND RESULTS: Sixty consecutive adult patients without suspected atriotomy-related AFL, congenital heart disease, or previous AFL ablation, referred for catheter ablation of presumed typical AFL were studied. All patients had distinct flutter waves in the inferior leads, suggestive of CTI-dependent AFL, either on presentation to the electrophysiology (EP) lab or documented on prior ECG. Electrophysiology study was performed in the standard fashion. Patients who presented to the EP laboratory not in AFL underwent arrhythmia induction with a burst pacing protocol. A clinical history of persistent AFL (P = 0.0001) and existence of AFL on presentation to the EP laboratory (P = 0.0001) were strong predictors of CTI dependence. History of atrial fibrillation (P = 0.19), structural heart disease (P = 0.6), hypertension (P = 0.4), and previous cardiac surgery (P = 0.5), as well as the nature of AFL-related symptoms (P = 0.5), were not predictors of CTI-dependent AFL documented during EP study. CONCLUSION: In patients with ECG suggestive of typical AFL, the presence of persistent rather than paroxysmal AFL and presentation to the EP laboratory in AFL are strong predictors of CTI-dependent AFL. A paroxysmal pattern of AFL predicts noninducibility of CTI-dependent AFL during EP study. CTI ablation may therefore be less effective in these patients.

Atrial volume reduction following catheter ablation of atrial fibrillation and relation to reduction in pulmonary vein size: an evaluation using magnetic resonance angiography.

INTRODUCTION: Catheter ablation to achieve pulmonary vein (PV) isolation has become an increasingly used treatment strategy for patients with atrial fibrillation (AF). The purpose of this study was to evaluate the impact of segmental isolation of PVs on volume of left atrium and its relation to the decrease in the size of the pulmonary veins. METHODS: Gadolinium enhanced Magnetic Resonance Angiography (MRA) was performed in 51 AF patients before and 6 approximately 8 weeks post PV isolation, using cooled radio-frequency (RF) energy. Three-dimensional reconstruction with maximum intensity projections and multiplanar reformations was performed. Oblique coronal projections were used to measure the ostial size of PVs. Three orthogonal dimensions of LA chamber were measured and computed to assess the volume of the left atrium. RESULTS: The mean LA volume decreased by 15.7% after ablation (p<0.001). The mean PV ostial diameter decreased by 11%, from 18.3+/-0.8 mm to 16.7+/-1.0 mm (p=0.005). Moderate PV stenosis was noted in two veins out of the 192 veins analyzed. There was a significant correlation between changes in the size of PV ostium to that of the LA. CONCLUSIONS: Catheter ablation of AF using a segmental PV isolation approach results in a significant reverse remodeling in the left atrium. Significant stenosis of PVs appears to be rare after the segmental isolation procedure.

Incidence and predictors of pulmonary vein stenosis following catheter ablation of atrial fibrillation using the anatomic pulmonary vein ablation approach: results from paired magnetic resonance imaging.

INTRODUCTION: There are currently no studies systematically evaluating pulmonary vein (PV) stenosis following catheter ablation of atrial fibrillation (AF) using the anatomic PV ablation approach. METHODS AND RESULTS: Forty-one patients with AF underwent anatomic PV ablation under the guidance of a three-dimensional electroanatomic mapping system. Gadolinium-enhanced magnetic resonance (MR) imaging was performed in all patients prior to and 8-10 weeks after ablation procedures for screening of PV stenosis. A PV stenosis was defined as a detectable (> or =3 mm) narrowing in PV diameter. The severity of stenosis was categorized as mild (<50% stenosis), moderate (50-70%), or severe (>70%). A total 157 PVs were analyzed. A detectable PV narrowing was observed in 60 of 157 PVs (38%). The severity of stenosis was mild in 54 PVs (34%), moderate in five PVs (3.2%), and severe in one PV (0.6%). All mild PV stenoses displayed a concentric pattern. Moderate or severe PV stenosis was only observed in patients with an individual encircling lesion set. Multivariable analysis identified individual encircling lesion set and larger PV size as the independent predictors of detectable PV narrowing. All patients with PV stenosis were asymptomatic and none required treatment. CONCLUSIONS: The results of this study demonstrate that detectable PV narrowing occurs in 38% of PVs following anatomic PV ablation. Moderate or severe PV stenosis occurs in 3.8% of PVs. The high incidence of mild stenosis likely reflects reverse remodeling rather than pathological PV stenosis. The probability of moderate or severe PV stenosis appears to be related to creation of individual encircling rather than encircling in pairs lesion.

Safety and efficacy of circumferential pulmonary vein catheter ablation of atrial fibrillation.

OBJECTIVES: The purpose of this study was to report the safety, efficacy, and predictors of recurrence of circumferential pulmonary vein (PV) catheter ablation in patients with atrial fibrillation (AF). BACKGROUND: Circumferential PV ablation has been described as an alternate ablation strategy for AF. METHODS: Seventy consecutive patients (age 56 +/- 10 years) with symptomatic drug refractory paroxysmal (n = 21), persistent (n = 22), and permanent (n = 27) AF underwent catheter ablation. The catheter ablation procedure was performed by creating circular lesions encircling right- and left-side PV ostia guided by an electroanatomic (CARTO) mapping system. Linear ablation lesions also were created in the cavotricuspid isthmus, the mitral isthmus, and in the posterior left atrium. In 42 patients (60%), additions linear lesions were created between superior and inferior PVs in a "figure-of-eight" fashion. RESULTS: At 6 +/- 2.5 months of follow-up, 53 patients (76%) were AF free, including 39 patients (56%) not taking and 14 patients (20%) taking antiarrhythmic drugs. Among various variables, only early recurrence of AF was a predictor of long-term recurrence. Significant complications included one pericardial tamponade, one stroke, and two PV occlusions. Both patients with PV occlusion received radiofrequency delivery in a figure-of-eight fashion. CONCLUSIONS: Circumferential PV catheter ablation of AF is associated with moderate efficacy and risk of complications. The absence of a difference in efficacy combined with the risk of PV stenosis associated with figure-of-eight lesion lead us to conclude that the figure-of-eight lesion should not be a routine component of circumferential PV AF ablation procedures.

Radiation exposure during catheter ablation of atrial fibrillation.

BACKGROUND: The purpose of this study was to determine the radiation exposure during catheter ablation of atrial fibrillation (AF) using the pulmonary vein (PV) approach. METHODS AND RESULTS: The study included 15 patients with AF and 5 patients each with atrial flutter and atrioventricular nodal reentrant tachycardia (AVNRT) who underwent fluoroscopically guided procedures on a biplane x-ray system operated at a low-frame pulsed fluoroscopy (7.5 frames per second). Radiation exposure was measured directly with 50 to 60 thermoluminescent dosimeters (TLDs). Peak skin doses (PSDs), effective radiation doses, and risk of fatal malignancies were all computed. Mean fluoroscopy durations for AF procedures were 67.8+/-21 minutes in the right anterior oblique (RAO) and 61.9+/-16.6 minutes in the left anterior oblique (LAO) projection, significantly different from that required for atrial flutter and AVNRT. The mean PSDs measured with the TLDs were 1.0+/-0.5 Gy in the RAO and 1.5+/-0.4 Gy in the LAO projection. The lifetime risk of excess fatal malignancies normalized to 60 minutes of fluoroscopy was 0.07% for women and 0.1% for men. CONCLUSIONS: The relatively small amounts of the patient's radiation exposure in this study, despite the prolonged fluoroscopy durations, can be attributed to the use of very-low-frame pulsed fluoroscopy, the avoidance of magnification, and optimal adjustments of the fluoroscopy exposure rates. The resulting lifetime risk of fatal malignancy is within the range previously reported for standard supraventricular arrhythmias.

Coronary vasospasm and myocardial infarction induced by oral sumatriptan.

Coronary vasospasm is well documented as a side effect of injectable subcutaneous forms of sumatriptan; only one such case has been reported so far with oral ingestion of sumatriptan in a patient with underlying coronary artery disease. This report describes a case of coronary vasospasm induced by oral sumatriptan even in normal coronary arteries. Physicians and patients should be aware of a small and unpredictable risk of the serious cardiac side effects of this drug.

Predictors of recurrence following catheter ablation of atrial fibrillation using an irrigated-tip ablation catheter.

INTRODUCTION: The aims of this study were to identify predictors of recurrence after catheter ablation of atrial fibrillation (AF) and to report the safety and efficacy of catheter ablation of AF using an irrigated-tip ablation catheter. METHODS AND RESULTS: Seventy-five consecutive patients (51 men [68%]; age 54 +/- 13 years) with symptomatic drug-refractory paroxysmal (42 patients), persistent (21 patients), or permanent (12 patients) AF underwent catheter ablation of AF using an irrigated-tip ablation catheter and a standard ablation strategy, which involved electrical isolation of all pulmonary veins (PVs) and creation of a cavotricuspid linear lesion. At 10.5 +/- 7.5 months of follow-up following a single (n = 75) or redo ablation procedure (n = 11), 39 (52%) of the 75 patients were free of AF, 10 were improved (13%), and 26 had experienced no benefit from the ablation procedure (35%). Seventy-six percent of patients with paroxysmal AF were free from recurrent AF. The most significant complications were two episodes of pericardial tamponade, mitral valve injury in one patient, two strokes, and complete but asymptomatic PV stenosis in one patient. Cox proportional hazards multivariate regression analysis identified the presence of persistent AF, permanent AF, and age >50 years prior to the ablation are the only independent predictors of AF recurrence after the first PV isolation procedure. CONCLUSION: Catheter ablation of AF using a strategy involving isolation of all PVs and creation of a linear lesion in the cavotricuspid isthmus using cooled radiofrequency energy is associated with moderate efficacy and an important risk for complications. The best results of this procedure are achieved in the subset of patients who are younger than 50 years and have only paroxysmal AF.

Characterization of a new pulmonary vein variant using magnetic resonance angiography: incidence, imaging, and interventional implications of the "right top pulmonary vein".

INTRODUCTION: Catheter ablation of the pulmonary veins (PVs) for prevention of recurrent atrial fibrillation requires precise anatomic information. We describe the characteristics of a new anatomic variant of PV anatomy using magnetic resonance angiography. METHODS AND RESULTS: A 1.5-T magnetic resonance imaging system with a body coil or a torso phased-array coil was used before and after gadolinium injection. Magnetic resonance angiograms were acquired with a breath-hold three-dimensional fast spoiled gradient-echo imaging sequence in the coronal plane. Three-dimensional reconstruction with maximum intensity projections and multiplanar reformations was performed. A newly described variant PV ascending from the roof of the left atrium was found in 3 of 91 subjects. The mean ostial diameter of the roof PV was 7 +/- 2 mm, the mean distance from the ostium to the first branching point was 22 +/- 8.5 mm, and the mean distance to the right superior PV was 3.3 +/- 0.6 mm. CONCLUSION: We refer to the newly described variant of PV anatomy as the "right top pulmonary vein." It is important to be aware of this anatomic pattern to avoid inadvertent catheter intubation, which can result in misleading mapping results and PV stenosis.

Technique and results of pulmonary vein angiography in patients undergoing catheter ablation of atrial fibrillation.

INTRODUCTION: Delineation of pulmonary vein (PV) anatomy is an integral part of the PV isolation procedure. The aims of the present study were to (1) describe the technique of selective PV angiography, (2) show the typical fluoroscopic locations and appearance of the PVs, and (3) compare the ostial diameters of PVs measured by angiography and magnetic resonance imaging (MRI). METHODS AND RESULTS: Twenty consecutive patients undergoing a PV isolation procedure underwent selective PV angiography using a deflectable 8-French lumened catheter (Naviport, Cardima). The left superior PV (LSPV) runs upward and away from the spine in the right anterior oblique (RAO) projection and upward and toward the spine in the left anterior oblique (LAO) projection. The opposite is true for the right superior PV (RSPV). The left inferior PV (LIPV) has a bull's-eye appearance in the RAO projection, and the right inferior PV (RIPV) has a bull's-eye appearance in the LAO projection due to their end-on trajectories. The LIPV in the LAO projection and the RIPV in the RAO projection run horizontally toward the spine. An excellent correlation was noted in PV ostial size as assessed by angiography and MRI (r(2) < 0.90, P < 0.0001). CONCLUSION: This study describes the technique and results of PV angiography and fluoroscopy. The study also demonstrates good correlation of PV ostial diameters by contrast venography and MRI. PV angiography can be used as an alternate to MRI or computed tomographic imaging, particularly when these tests are unavailable or are contraindicated in the patient.

Pulmonary vein occlusion: an unanticipated complication of catheter ablation of atrial fibrillation using the anatomic circumferential approach.

Favorable results of circumferential pulmonary vein (PV) ostial ablation guided by electroanatomic mapping (Carto) have fueled great enthusiasm for this technique. The lesion set for this ablation procedure as described by Pappone et al.(1,2) involves a figure of 8 lesions encompassing the 2 right and 2 left PV ostia with 2 additional linear lesions. Pulmonary vein stenosis/or occlusion has not previously been reported as a complication of this procedure. We describe PV occlusion after this procedure. Based on the occurrence of this previously unreported complication, we no longer create a figure '8' lesion around the right superior and inferior PVs. We anticipate that this complication can be avoided by creating a circular lesion encompassing the 2 PV ostia, while avoiding the linear lesion between the 2 PV ostia.

High defibrillation thresholds in transvenous biphasic implantable defibrillators: clinical predictors and prognostic implications.

The aim of this study was to identify clinical characteristics that distinguish patients with high DFTs and assess the prognostic implication. DFTs testing is a lengthy, potentially painful, and a hazardous process. Little information is available concerning the identification of patients with high DFT who undergo ICD surgery with transvenous leads and biphasic energy. This study analyzed 968 patients from two separate clinical studies who received a Medtronic cardioverter defibrillator from January 1995 through November 1999 and who had DFT testing measured by a binary search protocol. Compared to 865 patients with low defibrillation thresholds (< 18 J), the 103 patients with high thresholds (> or = 18 J) had a lower LVEF (34 +/- 16.7 vs 38.3 +/- 16.2%, P = 0.01), a worse NYHA functional class (23% Class I, 43% Class II, 29% Class III, 5% Class IV vs. 27% Class I, 55% Class II, 17% Class III, 1% Class IV, P < 0.0001), had bypass surgery less often (10.7 vs 27.5%, P < 0.0001), used amiodarone within the past 6 weeks (42.7 vs 27.2%, P = 0.002), and had a history of ventricular fibrillation more often (44.7 vs 33.1%, P = 0.02). Information concerning the number of shocks delivered was available in 345 (35%) patients; 23 were in the high DFT group and 322 were in the low DFT group. Twelve (52%) of the 23 patients in the high DFT arm received 3.6 +/- 2.7 shocks (median 2.5) and 106 (33%) of the 322 patients with low DFT received 4.9 +/- 9.5 shocks (median 2). After 6 months the mortality rate of patients with high thresholds was 11.7 vs 7.8% in patients with low thresholds (P = 0.118). Using a multivariate logistic regression model the significant predictors of death were older age, higher NYHA class, lower LVEF, amiodarone use, had a presenting arrhythmia of ventricular fibrillation and CHF but not initial high defibrillation thresholds. The study found that (1) 11% of patients have high DFTs, (2) clinical characteristics that identify high defibrillation thresholds are NYHA Class III, IV, low ejection fraction, no previous history of bypass surgery, prior amiodarone use preoperatively, and presenting with ventricular fibrillation, and (3) while high DFTs were associated with a more ill patient population, there was no difference in survival in a 6-month follow-up. Patients with a predicted low DFTs may be eligible for abbreviated ICD testing while high risk patients require formal testing.

Thrombus-in-transit and paradoxical embolism.

Paradoxical embolism is an uncommon but clinically important phenomenon. Elements of diagnosis include the presence of: (1) a venous thrombus, (2) an arterial embolus, (3) a communication between the right and left heart, and (4) a thrombus traversing such a communication. Unfortunately, all of these elements can be rarely demonstrated in each case but the probability should be considered in any patient with 2 or more present. It should be suspected in patients who have evidence of systemic arterial emboli without apparent cause. A transesophageal echocardiogram with contrast should be considered in cases where paradoxical embolism is a possibility. We present a case in which a "thrombus-in-transit" was imaged across the interatrial septum in a patient with a patent foramen ovale, deep venous thrombosis, and an embolic cerebrovascular stroke.