Magnetic resonance imaging abnormalities in the basal interventricular septum of patients with left ventricular outflow tract arrhythmias.

INTRODUCTION: Concealed structural abnormalities were detected by delayed enhancement - magnetic resonance imaging (DE-MRI) in patients with apparently idiopathic tachycardia of left ventricular (LV) origin. Basal septal fibrosis was evaluated as a potential arrhythmia substrate in patients with left ventricular outflow tract (LVOT) arrhythmias. METHODS AND RESULTS: A total of 22 patients with LVOT arrhythmias, including frequent monomorphic premature ventricular complexes (PVCs) in 15 patients and ventricular tachycardia (VT) in 7 patients, underwent catheter ablation and DE-MRI. A total of 19 patients with frequent PVCs and 17 patients with idiopathic VT of other origin served as a control group. Basal septal intramural fibrosis as thin strip-shaped intramyocardial DE or as marked intramyocardial DE involving >25% of wall thickness was detected more frequently in patients with LVOT arrhythmias (41% and 32%) than in patients with non LVOT arrhythmias (14% and 3%). After successful ablation, 4/16 patients with basal septal intramural fibrosis and LVOT PVCs (n = 3) or LVOT VT (n = 1) compared with no patient without basal septal fibrosis experienced episodes of sustained VT with similar or different QRS morphology resulting in ICD therapy in three patients. Follow-up DE-MRI after PVC ablation (17 ± 7 months) revealed an increase in LV ejection fraction from 49 ± 5% to 56 ± 5% (n = 9) but the amount of septal DE remained unchanged. CONCLUSIONS: Basal septal intramural fibrosis may serve as the arrhythmia substrate in a substantial part of patients with premature ventricular complexes (PVCs) and VT originating from the LVOT and identifies patients with continued risk for VT recurrence after initially successful ablation of LVOT arrhythmias.

Atypical Surface ECG Complicating the Diagnosis of Bundle Branch Reentry Tachycardia.

BACKGROUND: Typical left bundle branch block (LBBB) during ventricular tachycardia (VT) is a diagnostic criterion of bundle branch reentry tachycardia (BBRT) with activation of the right bundle in the anterograde direction. METHODS AND RESULTS: Eleven patients (seven male, 60 ± 12 years) with nonischemic cardiomyopathy (left ventricular ejection fraction 37 ± 16%) presenting with BBRT were successfully treated by ablation of the right bundle. Among them, five patients had atypical surface electrocardiograms (ECGs) differing from a typical LBBB during the VT. Three patients with severe enlargement and dysfunction of the left ventricle had broadened irregular QRS complexes with rR or RS configuration in lead V6 during the BBRT. Two patients with enlargement and/or hypokinesia of the right ventricle had entirely or almost entirely negative complexes (QS) in the chest leads (V1-V6) during the VT. Activation mapping in these two patients revealed that the exit site of the BBRT was in the anterior right ventricle generating a negative concordance in the precordial leads. CONCLUSIONS: Atypical surface ECGs with broadened irregular QRS complexes or negative concordance in the precordial leads can complicate the correct diagnosis of BBRT in patients with severe left ventricular dysfunction and involvement of the right ventricle.

Epicardial ventricular tachycardia substrate visualized by magnetic resonance imaging: need for a transpericardial ablation approach?

BACKGROUND: Sustained ventricular tachycardia (VT) in patients with nonischemic cardiomyopathy (NICM) often involves midmyocardial and epicardial structures. Delayed-enhancement magnetic resonance imaging (DE-MRI) of scar and fibrosis is the method of choice to define the substrate of monomorphic VT. OBJECTIVE: The aim of the study was to compare the outcome of endocardial vs. epicardial VT ablation in patients with epicardial DE-MRI substrates in NICM. RESULTS: Among 44 patients with NICM referred for VT ablation who underwent DE-MRI, 12 patients had an epicardial-only (n = 4) or predominantly epicardial DE-MRI substrate (n = 8). 9 of the 12 patients had a prior myocarditis. Endocardial-only VT ablation was successful in two patients with epicardial DE-MRI substrate. A pericardial access for epicardial mapping and ablation was attempted in 8 patients and could be accomplished in seven. Epicardial low voltage (<1.5 mV) and very low voltage (<0.5 mV) areas were in good qualitative correlation to the epicardial DE-MRI substrates. Epicardial abnormal electrograms in combination with a good pace map QRS match were found in epicardial very low voltage areas in five patients and in low voltage areas in two patients. 2 patients with endocardial-only ablation, five patients with endo-epicardial ablation and two patients with primary epicardial ablation had a favorable post-ablation outcome (follow-up 32 ± 26 months) but one patient had to undergo heart transplantation for heart failure deterioration. CONCLUSIONS: Endo-epicardial ablation or primary epicardial ablation should early be considered in patients after myocarditis or with other forms of nonischemic cardiomyopathy with epicardial DE-MRI substrates.

Lyme carditis--diagnosis, treatment and prognosis.

BACKGROUND: There are 60,000 to 100,000 new cases of borreliosis in Germany each year. This infectious disease most commonly affects the skin, joints, and nervous system. Lyme carditis is a rare manifestation with potentially lethal complications. METHODS: This review is based on selected publications on the clinical manifestations, diagnosis, and treatment of Lyme carditis, and on the authors' scientific and clinical experience. RESULTS: Lyme carditis is seen in 4% to 10% of all patients with Lyme borreliosis. Whenever the clinical suspicion of Lyme carditis arises, an ECG is mandatory for the detection or exclusion of an atrioventricular conduction block. Patients with a PQ interval longer than 300 ms need continuous ECG monitoring. 90% of patients with Lyme carditis develop cardiac conduction abnormalities, and 60% develop signs of perimyocarditis. Borrelia serology (ELISA) may still be negative in the early phase of the condition, but is always positive in later phases. Cardiac MRI can be used to confirm the diagnosis and to monitor the patient's subsequent course. The treatment of choice is with antibiotics, preferably ceftriaxone. The cardiac conduction disturbances are usually reversible, and the implantation of a permanent pacemaker is only exceptionally necessary. There is no clear evidence at present for an association between borreliosis and the later development of a dilated cardiomyopathy. When Lyme carditis is treated according to the current guidelines, its prognosis is highly favorable. CONCLUSION: Lyme carditis is among the rarer manifestations of Lyme borreliosis but must nevertheless be considered prominently in differential diagnosis because of the potentially severe cardiac arrhythmias that it can cause.

Findings on magnetic resonance imaging of fascicular ventricular tachycardia.

BACKGROUND: Idiopathic left ventricular tachycardia (ILVT) with right bundle branch block and left axis deviation originates from the left posterior fascicle--Purkinje fiber network. Scar-related ventricular tachycardias (VTs) with Purkinje fibers as a part of the reentry circuit have also been described in patients with structural heart disease. METHODS AND RESULTS: Nine patients with fascicular VT (left posterior, n = 8; left anterior, n = 1) with preserved left ventricular ejection fraction (60 ± 10%) underwent cardiac magnetic resonance imaging (MRI) including functional analysis and delayed enhancement magnetic resonance imaging (DE-MRI). No definite structural abnormalities were detected by DE-MRI in four patients. DE-MRI revealed unifocal or multifocal areas of fibrosis or scar in three patients corresponding to the regions where typical Purkinje potentials guided successful ablation of the sustained fascicular VT. A false tendon extending from the free wall to the septum was found in one patient. Moderate reduction of left ventricular ejection fraction associated with septal or multifocal left ventricular fibrosis was detected in two patients with ventricular bigeminy originating from the left posterior fascicle. During the follow-up of 29 ± 22 months after successful catheter ablation in the nine patients, one patient with septal fibrosis detected by DE-MRI had VT recurrence and received an implantable cardioverter defibrillator. CONCLUSION: Detection of local areas of fibrosis or scar by DE-MRI may help to distinguish idiopathic fascicular tachycardia from scar-related fascicular VT in patients with preserved left ventricular function.

The risk of delayed atrioventricular and intraventricular conduction block following ablation of bundle branch reentry.

BACKGROUND: The aim of the study was to determine the long-term reliability of atrioventricular and intraventricular conduction and the implications for cardiac resynchronization therapy (CRT-D) following catheter ablation of bundle branch reentry tachycardia (BBRT) and interfascicular tachycardia. METHODS AND RESULTS: Fourteen patients with recurrent monomorphic ventricular tachycardia (VT) (n = 11) and incessant VT (n = 3) underwent catheter ablation of BBRT (n = 7), interfascicular tachycardia (n = 5) or both arrhythmias (n = 2). Successful ablation was achieved in all patients without intraprocedural atrioventricular (AV) block. Within 2 months after ablation, three patients with BBRT and pre-existing prolonged QRS developed a delayed third-degree AV block. During the follow-up of 2 years, two patients with interfascicular tachycardia developed a new left bundle branch block (LBBB) associated with worsening of heart failure. Three patients underwent upgrading of implantable cardioverter defibrillator therapy to CRT-D early after ablation which improved heart failure during the 6 months follow-up. During the long-term follow-up of 39 ± 13 months, VT storm recurred in one patient. Four of the 14 patients died of deterioration of heart failure and one had to undergo heart transplantation. CONCLUSIONS: Catheter ablation for BBRT in patients with prolonged QRS is associated with a high risk of delayed third-degree AV block. Ablation of interfascicular tachycardia can be associated with delayed LBBB. After ablation of bundle branch reentry, patients with prolonged QRS are candidates for cardiac resynchronization therapy but the mortality remains high.

Myocardial perfusion imaging using OMNISCAN: a dose finding study for visual assessment of stress-induced regional perfusion abnormalities.

BACKGROUND: Different doses of contrast agent are applied for magnetic resonance perfusion studies and mainly semiquantitative approaches have been reported for analysis. We aimed to determine the optimal dose for a visual detection of perfusion defects. METHODS: 49 patients (59+/-8 years; 33 male) scheduled for invasive angiography were examined at stress (0.14 mg adenosine/kg body weight/minute) and rest using a TFE-EPI hybrid sequence (Philips ACS NT; 1.5 T). Patients were assigned to three different dose groups of gadodiamide (0.05, 0.1, and 0.15 mmol/kg body weight) injected as a bolus via a peripheral vein. Visual assessment was used to detect a regional reduction of peak signal intensity or speed of contrast agent inflow at stress in comparison to rest. RESULTS: Prevalence for coronary artery disease was 67%. The highest diagnostic accuracy was reached for a dose of 0.1 mmol gadodiamide/kg body weight (86% p=nonsignificant vs. 0.15 and 0.05 mmol gadodiamide/kg). At this dose, no major artifacts related to the contrast agent were found. CONCLUSIONS: Visual assessment of myocardial perfusion using a high-flow rate contrast agent bolus injection and a TFE-EPI sequence can be best achieved with a dose of gadodiamide 0.1 mmol/kg bodyweight.

Optimal acquisition parameters for contrast enhanced magnetic resonance imaging after chronic myocardial infarction.

The aim of this study was to simplify the imaging of myocardial infarction based on theoretical aspects and patient variables and to define the optimal time for image acquisition. Thirteen patients with chronic myocardial infarction underwent magnetic resonance imaging. After injection of 0.2 mmol/kg body weight Gd-DTPA an inversion recovery turbo gradient echo sequence with different prepulse delays was applied every 3 to 5 minutes within an interval of 3 to 30 minutes. As parameters of investigation, the area of signal enhancement and the contrast between enhanced and nonenhanced myocardium were used. There was no influence of prepulse delay or time after contrast injection on the enhanced area. The contrast between enhanced and normal myocardium showed a peak at 6 minutes post Gd-DTPA injection and remained high. The contrast between blood and enhanced myocardium was best at 6 and 25 minutes with best intra- and interobserver variability. In conclusion, if a suitable contrast was achieved, the area of enhancement is independent of prepulse delay or imaging time. In most patients the highest contrast between blood, enhanced and normal myocardium is achieved 6 minutes and 25 minutes after contrast injection.