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Biomedical subjects

Francis E Marchlinski

Publications and source records attributed to Francis E Marchlinski.

At least 55 records · Page 3Linked to original sources
PubMed2004

Mechanisms underlying sustained firing from pulmonary veins: evidence from pacing maneuvers and pharmacological manipulation.

Atrial Fibrillation (AF) is often initiated by pulmonary vein (PV) depolarizations. However, sustained PV firing (PVF) is infrequently observed in this population and has not been characterized. In 15 patients undergoing AF ablation we report the response of sustained PVF to pacing and pharmacological maneuvers. Sustained PVF was defined as discrete, repetitive, electrical activity during sinus rhythm that did not correspond with other electrical events (P, QRS, T wave), persisting > or =5 minutes and recorded at/or distal to PV ostium prior to ablation. During sustained PVF, pacing was performed from coronary sinus and/or posterior right atrium at different cycle lengths (900 to 400 ms; duration: 30 to 60 s) following which, if PVF persisted, in random order, isoproterenol and adenosine were administered and carotid sinus massage (CSM) was performed. PVF response was classified as: suppressed (complete quiescence), augmented (increase in frequency of PVF/AF initiation) and "no effect." Sustained PVF was observed in 16 veins. In 13 (81%) patients, PVF was suppressed during overdrive pacing with early recurrence (< or =5 s) postpacing regardless of pacing cycle length in 11 (85%) patients. PVF was augmented by isoproterenol in the majority of patients (88%) and showed mixed response to adenosine (augmented 40%, suppressed 20%, and no effect 40%). CSM appeared to have no effect on PVF in the majority of patients (86%). Sustained PVF is seen infrequently in patients undergoing AF ablation. Its response to pacing maneuvers argues against sustained reentry and supports triggered activity and/or abnormal automaticity as the mechanisms underlying the phenomenon.

Adenosine↗
PubMed2003

Characterization of endocardial electrophysiological substrate in patients with nonischemic cardiomyopathy and monomorphic ventricular tachycardia.

BACKGROUND: Although catheter mapping has been used to define the endocardial electrogram characteristics in patients with ventricular tachycardia (VT) and coronary disease, characterization of the electrophysiological substrate in patients with VT and nonischemic cardiomyopathy is limited. METHODS AND RESULTS: Left ventricular endocardial electroanatomical mapping was performed in 19 patients with nonischemic cardiomyopathy and monomorphic VT with an average of 178+/-83 sites per chamber mapped. Abnormal bipolar electrogram was defined as endocardial voltage signal amplitude of <1.8 mV. The extent and location of abnormal endocardium was estimated by measuring areas of abnormal electrogram recordings from 3D voltage maps. The origin of VT was approximated by identifying sites of entrainment with concealed fusion or early presystolic activity and/or by pace mapping. Abnormal electrograms were recorded over a 41+/-28 cm2 area that represented 20+/-12% of total endocardial surface. The majority of patients (14/19 patients) had only a modest area (<25%) of endocardial abnormality. All patients had abnormal low-voltage endocardial areas located near the ventricular base in the perivalvular region. There were 3+/-1 VT morphologies per patient. The majority (88%) of the 57 mapped VTs originated from the ventricular base, corresponding to regions with abnormal endocardial electrograms. CONCLUSIONS: Electroanatomical mapping in patients with monomorphic VT and nonischemic cardiomyopathy typically demonstrates a modest-sized basal area of endocardial electrogram abnormalities. The VT site of origin corresponds to these basal electrogram abnormalities. These findings have important implications regarding strategies for VT ablation in this setting.

Adult↗
PubMed2003

Quantitative comparison of spontaneous and paced 12-lead electrocardiogram during right ventricular outflow tract ventricular tachycardia.

OBJECTIVES: The purpose of this study was to objectively quantify the similarity of 12-lead electrocardiogram (ECG) waveforms using two quantitative metrics, the correlation coefficient (CORR) and the mean absolute deviation (MAD). BACKGROUND: Comparison of the 12-lead ECG morphology between ventricular tachycardia (VT) and a pace-map is frequently performed; however, there are no objective criteria for quantifying the similarity between two waveform morphologies. METHODS: During ablation of right ventricular outflow tract (RVOT) VT, 12-lead ECG pace-maps were acquired from three superior septal sites, three superior free wall sites, and before each ablation attempt in 15 patients. The 12-lead ECG waveforms of the clinical tachycardia and pace-maps were compared using both MAD and CORR at each site. RESULTS: The MAD scores were lower (i.e., more closely matched) for septal compared with free wall sites (15.9 +/- 5.3% vs. 25.3 +/- 10.2%; p < 0.001). Successful ablation sites had a significantly lower MAD score compared with unsuccessful sites (9.5 +/- 2.8% vs. 13.3 +/- 5.6%; p = 0.01), whereas there was only a trend toward a higher CORR for successful ablation sites (98.2 +/- 1.2% vs. 96 +/- 4.7%; p = 0.07). A MAD score < or =12% was 93% sensitive and 75% specific for identifying a successful ablation site. There was an inverse correlation between MAD score and distance from the site of VT origin (r = 0.63, p < 0.001). CONCLUSIONS: A MAD score >12% between RVOT VT and a pace-map at any site suggests sufficient dissimilarity to dissuade ablation at that site. The MAD score can be used to standardize 12-lead ECG waveform morphology comparisons among different laboratories, and may be useful for guiding ablation of VT.

Adult↗
PubMed2003

Advances in ablation therapy for complex arrhythmias: atrial fibrillation and ventricular tachycardia.

Catheter ablation has evolved over the past two decades to become first-line therapy for many cardiac arrhythmias. Multiple advances in the technology and understanding of radiofrequency ablation have allowed this technique to blossom into one of the most powerful therapeutic tools available to the electrophysiologist, and have opened a new chapter in the diagnosis and management of clinical arrhythmias. Catheter ablation often eliminates the need for chronic drug therapy and can result in significant long-term cost savings. As catheter technology continues to improve, and newer, more effective energy delivery systems are developed, the applicability of catheter-based therapy will continue to expand. This review addresses some of the more commonly encountered clinical arrhythmias and the recent developments in the treatment of these arrhythmias from a catheter-based standpoint.

Arrhythmias, Cardiac↗
PubMed2003

Change in distant atrial activation patterns during circumferential pacemapping of pulmonic vein ostium: implications for localizing triggers for atrial fibrillation.

INTRODUCTION: Unique intracardiac activation patterns recorded from multipolar catheters in the coronary sinus (CS) and posteromedial right atrium (RA) when pacing from ostium (os) of each pulmonic vein (PV) can serve as template for determining PV of origin of atrial premature complexes. Development of an accurate template requires knowledge of variations in activation pattern during pacing from different aspects of same PV. METHODS: In 25 patients undergoing catheter ablation for AF, a decapolar Lasso mapping catheter was placed at PV os of interest and multipolar catheters were placed in CS and RA-medial to crista terminalis (CT). For each PV, pacing was performed from Lasso catheter poles 1 through 10. For each bipole paced, activation sequence in CS (proximal to distal & vice-versa) was assessed, activation time (pacing stimulus to earliest electrogram recorded in catheters in CS/along CT) was measured and difference (CS - CT time) was determined. Significant interpolar variation was defined as the difference between the shortest and longest CS - CT activation time of >/=25 msec when pacing from different bipoles of same PV. RESULTS: In 59 PVs [19 right superior (RS), 20 left superior (LS), 8 right inferior (RI) and 12 left inferior (LI)], 259 bipoles were paced (median of 4 bipoles/PV). During circumferential PV pacing activation sequence in CS catheter was distal to proximal in 84.4% left-sided PVs (LSPV and LIPV) and proximal to distal in 92.6% right-sided PVs (RSPV and RIPV) with no change in activation sequence observed during pacing from different bipoles in same PV. Significant interpolar variation was observed with circumferential pacing in 1 of 19 RSPV (5.3%), 2 of 20 LSPV (10%), 1 of 12 LIPV (8.3%) and none of RIPV. CONCLUSION: Unique intracardiac activation patterns during ostial pacing from individual PV are not influenced by circumferential location of pacing site.

Atrial Fibrillation↗
PubMed2003

Atrial tachycardia successfully treated by electrical isolation of the superior vena cava.

This case report describes a patient with an atrial tachycardia that was difficult to induce and that originated from the superior vena cava. Although the patient had frequent episodes of tachycardia, the tachycardia induced in the electrophysiological laboratory was nonsustained and could not be adequately localized for focal ablation. A circumferential mapping catheter was used to guide electrical isolation of the superior vena cava from the right atrium, curing the tachycardia. Electroanatomic mapping and intracardiac echocardiography were used to monitor the ablation and document patency of the superior vena cava throughout the ablation.

Adult↗
PubMed2003

Electrocardiographic patterns of superior right ventricular outflow tract tachycardias: distinguishing septal and free-wall sites of origin.

INTRODUCTION: The superior right ventricular outflow tract (RVOT) septum and free wall are common locations of origin for outflow tract ventricular tachycardias (VT). We hypothesized that (1) unique ECG morphologies of pace maps from septal and free-wall sites in the superior RVOT could be identified using magnetic electroanatomic mapping for accurate anatomical localization; and (2) this ECG information could help facilitate pace mapping and accurate VT localization. METHODS AND RESULTS: In 14 patients with structurally normal hearts who were undergoing ablation for outflow tract VT, a detailed magnetic electroanatomic map of RVOT was constructed in sinus rhythm, then pace mapping was performed from anterior, mid, and posterior sites along the septum and free wall of the superior RVOT. Pace maps were analyzed for ECG morphologies in limb leads and transition patterns in precordial leads. Monophasic R waves in inferior leads for septal sites were taller (1.7 +/- 0.4 mV vs 1.1 +/- 0.3 mV; P < 0.01) and narrower (158 +/- 21 msec vs 168 +/- 15 msec; P < 0.01) compared with free-wall sites; lacked "notching" (28.6% vs 95.2%; P < 0.05); and showed early precordial transition (by lead V4; 78.6% vs 4.8%; P < 0.05). A positive R wave in lead I also distinguished posterior from anterior septal and free-wall sites. Based on QRS morphology in limb leads and precordial transition pattern (early vs late), in a retrospective analysis, a blinded reviewer was able to accurately localize the site of origin of clinical arrhythmia (the successful ablation site on the magnetic electroanatomic map) in 25 of 28 patients (90%) with superior RVOT VT. CONCLUSION: Pace maps in the superior RVOT region manifest site-dependent ECG morphologies that can help in differentiating free-wall from septal locations and posterior from anterior locations. Despite overlap in QRS amplitude and duration, in the majority of patients a combination of ECG features can serve as a useful template in predicting accurately the site of origin of clinical arrhythmias arising from this region.

Adult↗
PubMed2003

Efficacy and safety of targeted focal ablation versus PV isolation assisted by magnetic electroanatomic mapping.

INTRODUCTION: Pulmonary vein (PV) triggers initiate atrial fibrillation (AF). The aim of this study was to compare the outcome of focal PV ablation versus targeted PV electrical isolation aided by multipolar catheter recordings in the coronary sinus (CS) and right atrium and magnetic electroanatomic mapping (MEAM) for drug-refractory AF. METHODS AND RESULTS: Multipolar recordings identified PVs with triggers based on PV ostial pace map match for spontaneous and provoked triggers. PV triggers were provoked by isoproterenol, adenosine, and AF induction followed by cardioversion. MEAM defined PV ostial anatomy and assisted in localization of AF trigger and ablation lesions. All focal PV ablation procedures preceded PV isolation procedures at our institution. To limit a learning curve effect and validate the comparison, the results included outcome of procedures by a single experienced operator in the last 32 consecutive patients undergoing focal PV ablation and in 75 consecutive patients undergoing PV isolation. Patient characteristics were similar with respect to mean age (50 vs 52 years), mean left atrial size (4.3 vs 4.2 cm), presence of paroxysmal AF (84% vs 88%), and demonstration of non-PV triggers (16% in both groups). PV isolation was confirmed in 99% of PVs by multipolar circular catheter. MEAM confirmed noncircumferential ostial ablation in 69% of PVs. Patients undergoing PV isolation had less AF from PV triggers at the end of ablation (1% vs 16%, P < 0.01); had less AF at 2 months (17% vs 42%, P < 0.001); and had 1-year freedom from AF of 80% versus 45% (P < 0.001). Adverse events were low in both groups with no stroke or symptomatic PV stenosis. CONCLUSION: Using the described techniques, PV electrical isolation of PVs demonstrating spontaneous and/or provoked triggers is superior to focal PV ablation, with marked differences in outcome by 2 months. MEAM confirmed the noncircumferential nature of ostial ablation for effective isolation of most PVs and may play a role in the low risk and good outcome observed. The good outcome of targeted PV isolation as described suggests the need for a prospective comparison of targeted versus empiric PV isolation techniques.

Aged↗
PubMed2003

Incidence and location of focal atrial fibrillation triggers in patients undergoing repeat pulmonary vein isolation: implications for ablation strategies.

INTRODUCTION: The etiology of atrial fibrillation (AF) recurrences after pulmonary vein (PV) isolation is not well described. The aim of this study was to examine the reason for recurrent AF in patients undergoing a repeat attempt at AF trigger ablation. METHODS AND RESULTS: Patients with recurrent AF more than 1 month after ablation returned for repeat mapping and ablation. A circular mapping catheter was advanced to each previously targeted PV ostium to determine if the PV was still electrically isolated. Ectopy then was provoked with isoproterenol (up to 20 microg/min), burst pacing, and pacing into AF followed by cardioversion. The location of ectopy triggering atrial premature depolarizations (APDs) or AF was noted. Of 226 patients who underwent ablation of AF triggers, 34 (8 women and 26 men; age 56 +/- 10 years) with recurrent AF returned for a repeat procedure 207 +/- 183 days after the first procedure. There were 84 previously completely isolated PVs in these 34 patients. Thirty-three (39%) of 84 previously isolated PVs were still completely isolated at the time of the second procedure. Fifty-one PVs (61%) had evidence of recovered PV potentials. Fifty triggers of APDs and AF (n = 30) or APDs only (n = 20) were identified in these 34 patients. The majority of triggers [27/50 (54%)] originated from previously targeted PVs. Sixteen triggers [16/50 (32%)] originated from previously nontargeted PVs. CONCLUSION: The majority of AF recurrences originate from previously isolated PVs. One third of recurrent triggers originated from PVs that were not targeted during the initial ablation session. Although empiric isolation of all PVs may reduce recurrences, strategies to ensure ostial PV isolation and to prevent recurrent PV conduction after ablation should have the greatest impact on reducing AF recurrence.

Atrial Fibrillation↗
PubMed2003

Implantable cardioverter defibrillator events in patients with asymptomatic nonsustained ventricular tachycardia: is device implantation justified?

Primary prevention trials have demonstrated that patients with coronary disease, reduced left ventricular function, and nonsustained ventricular tachycardia (NSVT) have improved survival with implantable cardioverter defibrillator (ICD) therapy, presumably secondary to effective termination of life-threatening arrhythmias. However, stored intracardiac electrograms were not always available and specific arrhythmias leading to ICD therapy were not always known. We examined the occurrence of ICD events in 51 consecutive patients who match the described patient profile to determine the frequency of appropriate and inappropriate ICD therapy. ICD detections were noted in 18 (35%) patients during a median follow-up period of 13.1 months. Appropriate therapy for sustained ventricular tachycardia (VT)/ventricular fibrillation (VF) occurred in 11 (22%) patients, with appropriate shocks in 8 (16%) patients and appropriate antitachycardia pacing (ATP) in 4 (8%) patients. The time to first appropriate therapy occurred at a mean of 17 +/- 12 months (median 18 months, range 3-36 months). Inappropriate therapy occurred in 5 (10%) patients with inappropriate shocks in 4 patients and inappropriate ATP in 2 patients. Inappropriate therapy was delivered for supraventricular arrhythmias (SVAs) in 4 patients and for T wave oversensing in 1 patient. The reason for shock therapy was unknown in 1 patient (2%) due to ICD malfunction. The mean arrhythmia rate leading to appropriate therapy for VT/VF was 232 +/- 72 beats/min (range 181-400 beats/min), and the mean rate leading to inappropriate therapy for SVT was 168 +/- 10 beats/min (range 160-180 beats/min). Patients with coronary disease and asymptomatic NSVT commonly receive appropriate defibrillator therapy. These results support the need for ICD implantation for primary prevention, with attention to careful programming of the detection rate to prevent inappropriate therapy.

Aged↗
PubMed2002

Interactions of antiarrhythmic drugs and implantable devices in controlling ventricular tachycardia and fibrillation.

Implantable cardioverter defibrillators (ICDs) have proven highly successful in the treatment of life-threatening ventricular arrhythmias. Despite the efficacy of the ICD in terminating ventricular arrhythmias, antiarrhythmic drugs remain an important adjunct to ICD therapy. The use of antiarrhythmic drug therapy in combination with the ICD is synergistic in terms of beneficial effects, but also has the potential for some adverse interactions. Knowledge and recognition of these potential interactions is important for any physician managing patients with an ICD. This review summarizes the benefits and adverse effects of ICD in combination with antiarrhythmic drug therapy, and provides guidelines to ensure safe application of this hybrid therapy.

Anti-Arrhythmia Agents↗
PubMed2002

Electrophysiology studies in patients with dilated cardiomyopathies.

Dilated cardiomyopathy is a diverse group of heart diseases with variable arrhythmia substrates. The response to programmed stimulation is dependent on spontaneous arrhythmia presentation. In patients with dilated cardiomyopathy, the majority of sustained monomorphic VT is caused by a scar-related reentrant mechanism, similar to that of coronary artery disease. The arrhythmia is uniformly inducible and is often refractory to pharmacologic therapy. Sustained VT is associated with more extensive myocardial fibrosis and non-uniform anisotropy, involving both the endocardium and epicardium, compared to those without sustained reentry. The response to programmed stimulation is more variable in patients presenting with nonsustained arrhythmia, cardiac arrest or syncope. Inducibility of monomorphic VT is much lower compared to those with ischemic heart disease. Other non-reentrant mechanism, such as focal automaticity, can also be observed in patients with monomorphic VT, in the absence of myocardial scar or evidence of slow conduction. The utility of electrophysiology studies to determine prognosis and to guide therapy remains limited in this patient population. The clinical outcome does not correlate with arrhythmia inducibility, and suppression of induced arrhythmia does not predict a good prognosis. The diagnosis of sarcoidosis or Chagas' cardiomyopathy should be considered in patients with dilated cardiomyopathy of unknown etiology, particularly in those with marked regional wall motion abnormalities and inducible VT. Epicardial reentrant circuits may be more prevalent in these cardiomyopathies, especially in those with VT related to chronic Chagas' disease. Although bundle branch reentry VT is a common finding in patients with dilated cardiomyopathy, it can occur in cardiomyopathy of any type and may coexist with other myocardial reentrant VT. It often has a typical bundle branch block QRS pattern during VT and is associated with His-Purkinje conduction delay. Evidence of macroreentry involving the bundle branches can usually be demonstrated, and catheter ablation of the bundle branches provides an effective and specific treatment.

Bundle-Branch Block↗
PubMed2002

A comparison of left atrial size by two-dimensional transthoracic echocardiography and magnetic endocardial catheter mapping.

This study sought to validate the accuracy of magnetic electroanatomic mapping (MEAM) for determining cardiac chamber size in a clinically relevant situation. The authors chose to compare LA size measured by MEAM to that assessed by two-dimensional guided M-mode echocardiography. The study included 37 patients with drug refractory paroxysmal atrial fibrillation who underwent two-dimensional echocardiography and a detailed MEAM of the LA. The entire LA was mapped with a mean of 132 +/- 50 points with attention to identifying the mitral annulus and posterior wall of the LA. The MEAM measurement of LA size was taken as the distance from the anterior wall of the LA to the posterior wall in a plane parallel to the mitral valve annulus at atrial end-diastole. LA dimension determined by M-mode echocardiography was assessed in a plane parallel to the mitral valve annulus in the parasternal long-axis view during atrial end-diastole. LA size assessed by M-mode echocardiography was 41.2 +/- 5.0 versus 40.9 +/- 4.5 mm as assessed by MEAM, with good correlation (r = 0.87, P < 0.001). Only three patients had a difference in LA size that was > 0.3 cm between the two measurement techniques. Thus, it appears that LA anteroposterior dimension as determined by electroanatomic mapping is similar to that determined by two-dimensional guided M-mode echocardiography. MEAM appears to be an accurate method by which LA size can be assessed in patients with drug refractory atrial fibrillation undergoing left atrial ablation procedures.

Adult↗
PubMed2002

Characterization of the electroanatomic substrate for monomorphic ventricular tachycardia in patients with nonischemic cardiomyopathy.

Ventricular arrhythmias are common in the setting of nonischemic cardiomyopathy. The etiology for the cardiomyopathy is frequently not identified and the label of "idiopathic" is applied. Interstitial fibrosis with conduction system involvement and associated left bundle branch block characterizes the disease process in some patients and the mechanism for monomorphic ventricular tachycardia is commonly bundle branch reentry. However, most patients with nonischemic cardiomyopathy have VT due to myocardial reentry and demonstrate marked myocardial fibrosis and electrogram abnormalities. Although patient specific, the overall distribution of electroanatomic abnormalities appears to be equal on the endocardium and epicardium. The extent of electrogram abnormalities appears to parallel arrhythmia presentation and/or inducibility. Patients with sustained uniform morphology VT have the most extensive endocardial and epicardial electrogram abnormalities. Magnetic electroanatomic voltage mapping provides a powerful tool to characterize the location and extent of the arrhythmia substrate. Basal left ventricular myocardial involvement, as indexed by the location of contiguous electrogram abnormalities, is common in patients with sustained VT and left ventricular cardiomyopathy. The relatively equal distribution of electrogram abnormalities on the endocardium and epicardium, and the results of mapping and ablation attempts, suggest that critical parts of the reentrant circuit may be epicardial. Unique features of the electroanatomic substrate associated with cardiomyopathy due to Chagas' disease, sarcoidosis, and arrhythmogenic right ventricular dysplasia are also discussed.

Cardiomyopathies↗
PubMed2002

Utility of exit block for identifying electrical isolation of the pulmonary veins.

INTRODUCTION: Electrical isolation of the pulmonary veins (PVs) to treat paroxysmal atrial fibrillation (AF) has been described using "entry block" as an endpoint for PV isolation. We describe a new technique for guiding PV isolation, using "exit block" out of the PV after ablation as a criterion for successful isolation. METHODS AND RESULTS: A circular mapping catheter was positioned at the os of arrhythmogenic PVs and ablation was performed proximal to the mapping catheter until entry block into the vein was achieved. Pacing was performed from the mapping catheter and from the ablator inside the PV to document exit block out of the PV. In patients in whom cardioversion did not restore sinus rhythm, PV isolation was performed in AF. Entry and exit block were reassessed in ablated veins after a 20-minute waiting period. Ninety-five PVs were ablated in 41 patients. A total of 66 PVs in 34 patients were ablated in sinus rhythm. After entry block was achieved, exit block was present in only 38 (58%) of 66 PVs. A total of 29 PVs in 21 patients were ablated in AF. After cardioversion to sinus rhythm, there was evidence of entry block into the PV in 20 (69%) of 29 PVs and exit block in only 14 (48%) of 29 PVs. There was no significant difference between the total number of lesions applied per vein in sinus rhythm compared with AF (11.6 +/- 8.6 vs 10.3 +/- 6.2; P = NS). There was recovery of conduction after a 20-minute waiting period in 9 (11%) of 84 PVs. CONCLUSION: Identification of exit block after ostial PV ablation provides a clear endpoint for electrical isolation of the PVs. Isolation of the PVs can be performed during sustained AF without the need to apply excess RF lesions. Applying a 20-minute waiting period after electrical isolation will identify reconnection in approximately 10% of PVs.

Adult↗