Histopathology of conducting system in left anterior hemiblock. (1/664)

In 8 cases of left anterior hemiblock, combined with right bundle-branch block in 7, serial sections of the conducting system of the heart were examined histologically. In all cases there were pathological changes in the left bundle-branch but the anterior part of it was predominantly affected in only 2 cases. Acute changes were found in 6 cases of early myocardial infarction, and fibrosis in 2 cases of chronic heart disease. Reversible lesions may have a pathogenetic role in acute hemiblocks. The right bundle-branch was disrupted by fibrosis in 6 of the 7 cases with right bundle-branch block, and minor changes in the AV node were observed in 1. The widespread damage to the left bundle-branch in the majority of the present cases does not seem to be consistent with the limited clinicopathological correlation implied by the terms anterior fascicular block or hemiblock. Other cardiac lesions within the left bundle-branch and outside it may contribute to this electrocardiographic pattern.  (+info)

Incomplete right bundle branch block and vital capacity. (2/664)

Right bundle branch block (RBBB) is occasionally encountered in young persons who lack any other evidence of overt cardiac disease (Hiss and Lamb, 1962; Lancaster, Schechter, and Massing, 1972). The block may be complete or incomplete, the latter being more common. Right bundle branch block has been studied in relation to body weight, obesity, serum cholesterol and glucose levels, and blood pressure, but the results have been negative (Ostrander, 1964; Kannel et al., 1962). Data presented here suggest that incomplete RBBB is related to vital capacity.  (+info)

Phasic coronary flow pattern and flow reserve in patients with left bundle branch block and normal coronary arteries. (3/664)

OBJECTIVES: The purpose of this study was to determine whether scintigraphic myocardial perfusion defects in patients with left bundle branch block (LBBB) and normal coronary arteries are related to abnormalities in coronary flow velocity pattern and/or coronary flow reserve. BACKGROUND: Septal or anteroseptal defects on exercise myocardial perfusion scintigraphy are common in patients with LBBB and normal coronary arteries. METHODS: Thirteen patients (7 men, age 61+/-8 years) with LBBB and normal coronary arteries underwent stress thallium-201 scintigraphy and cardiac catheterization. In all patients and in 11 control subjects coronary blood flow parameters were calculated from Doppler measurements of flow velocity in the left anterior descending coronary artery (LAD) before and after adenosine administration. RESULTS: The time to maximum peak diastolic flow velocity was significantly longer both for the seven patients with (134+/-19 ms) and for the six without (136+/-7 ms) exercise perfusion defects than for controls (105+/-12 ms, p < 0.05), whereas the acceleration was slower (170+/-54, 186+/-42 and 279+/-96 cm/s2, respectively, p < 0.05). Coronary flow reserve in the patients with exercise perfusion defects (2.7+/-0.3) was significantly lower than in those without (3.7+/-0.5, p < 0.05) or in the control group (3.4+/-0.5, p < 0.05). CONCLUSIONS: Patients with LBBB have an impairment of early diastolic blood flow in the LAD due to an increase in early diastolic compressive resistance resulting from delayed ventricular relaxation. Furthermore, exercise scintigraphic perfusion defects in these patients are associated with a reduced coronary flow reserve, indicating abnormalities of microvascular function in the same vascular territory.  (+info)

Radiofrequency catheter ablation of coexistent atrioventricular reciprocating tachycardia and left ventricular tachycardia originating in the left anterior fascicle. (4/664)

Coexistence of supraventricular tachycardia and ventricular tachycardia is rare. A patient with no structural heart disease and wide QRS complex tachycardia with a right bundle block configuration and right-axis deviation underwent electrophysiological examination. A concealed left atrioventricular pathway (AP) was found, and atrioventricular reciprocating tachycardia (AVRT) and left ventricular tachycardia (VT) originating in or close to the anterior fascicle of the left ventricle were both induced. Radiofrequency (RF) catheter ablation of the concealed left AP was successfully performed. Ten months later, VT recurred and was successfully ablated using a local Purkinje potential as a guide. Coexistent AVRT and idiopathic VT originating from within or near the left anterior fascicle were successfully ablated.  (+info)

The circadian pattern of the development of ventricular fibrillation in patients with Brugada syndrome. (5/664)

AIMS: Brugada syndrome is considered to be a distinctive subgroup of idiopathic ventricular fibrillation. Identification of the circadian pattern of ventricular fibrillation would contribute to the elucidation of its underlying pathophysiology, but this pattern remains unknown in patients with Brugada syndrome. METHODS: and Results A total of 12 consecutive Brugada syndrome patients (46+/-14 years, all male) who underwent implantation of an implantable cardioverter defibrillator were studied. The distribution of the time of ventricular fibrillation detection was examined and classified into four 6-hour time periods of the day. The mean follow-up period following implantation was 777+/-535 days. In six out of the 12 patients, ventricular fibrillation occurred during follow-up. The data logs revealed that ventricular fibrillation was detected 30 times (range, 3-9). Ventricular fibrillation was observed more frequently at night ( 1800 h to 0600 h) than in the day (0600 h to 1800 h) (93.3% [28/30] vs 6.7%[2/30], P<0.001), and during sleep than while awake (86.7% [26/30] vs 13.3%[4/30], P<0.001). Ventricular fibrillation occurred most frequently between midnight and 0600 h in patients with ventricular fibrillation episodes during sleep (76.9% [20/26] vs 23.1%[6/26], P<0.01). CONCLUSION: These results suggest that increased nocturnal vagal activity and withdrawal sympathetic activity may play an important role in the arrhythmogenesis of the Brugada syndrome.  (+info)

Significance of late diastolic potential preceding Purkinje potential in verapamil-sensitive idiopathic left ventricular tachycardia. (6/664)

BACKGROUND: Verapamil-sensitive idiopathic left ventricular tachycardia (VT) is due to reentry with an excitable gap. A late diastolic potential (LDP) is recorded during endocardial mapping of this VT, but its relation to the reentry circuit and significance in radiofrequency (RF) ablation remain to be elucidated. METHODS AND RESULTS: Sixteen consecutive patients with this specific VT were studied (12 men and 4 women; mean age, 32 years). In all patients, sustained VT was induced and during left ventricular endocardial mapping, LDP preceding Purkinje potential (PP) was recorded at the basal (11 patients), middle (3 patients), or apical septum (2 patients). The area with LDP recording was confined to a small region (0.5 to 1.0 cm2) in each patient and was included in the area where PP was recorded (2 to 3 cm2). The relative activation times of LDP, PP, and local ventricular potential (V) at the LDP recording site to the onset of QRS complex were -50.4+/-18.9, -15.2+/-9.6, and 3.0+/-13.3 ms, respectively. The earliest ventricular activation site during VT was identified at the posteroapical septum and was more apical in the septum than the region with LDP in every patient. In 9 patients, VT entrainment was done by pacing from the right ventricular outflow tract while recording LDP. During entrainment, LDP was orthodromically captured, and as the pacing rate was increased, the LDP-to-PP interval was prolonged, whereas stimulus-to-LDP and PP-to-V interval were constant. In 3 patients, the pressure applied to the catheter tip at the LDP region resulted in conduction block between LDP and PP and in VT termination. RF energy application at the LDP recording site successfully eliminated VT. CONCLUSIONS: LDP was suggested to represent the excitation at the entrance to the specialized area with a conduction delay in response to the increase in the rate within the critical slow conduction zone participating in the reentry circuit of this VT. LDP can be a useful marker for successful RF ablation for this VT.  (+info)

Mapping of regional myocardial strain and work during ventricular pacing: experimental study using magnetic resonance imaging tagging. (7/664)

OBJECTIVES: The purpose of this study was to determine the spatial distribution of myocardial function (myofiber shortening and work) within the left ventricular (LV) wall during ventricular pacing. BACKGROUND: Asynchronous electrical activation, as induced by ventricular pacing, causes various abnormalities in LV function, perfusion and structure. These derangements may be caused by abnormalities in regional contraction patterns. However, insight into these patterns during pacing is as yet limited. METHODS: In seven anesthetized dogs, high spatial and temporal resolution magnetic resonance-tagged images were acquired in three orthogonal planes. Three-dimensional deformation data and LV cavity pressure and volume were used to determine midwall circumferential strain and external and total mechanical work at 192 sites around the left ventricle. RESULTS: During ventricular pacing, systolic fiber strain and external work were approximately zero in regions near the pacing site, and gradually increased to more than twice the normal value in the most remote regions. Total mechanical work, normalized to the value during right atrial pacing, was 38 +/- 13% (right ventricular apex [RVapex] pacing) and 61 +/- 23% (left ventricular base [LVbase] pacing) close to the pacing site, and 125 +/- 48% and 171 +/- 60% in remote regions, respectively (p < 0.05 between RVapex and LVbase pacing). The number of regions with reduced work was significantly larger during RVapex than during LVbase pacing. This was associated with a reduction of global LV pump function during RVapex pacing. CONCLUSIONS: Ventricular pacing causes a threefold difference in myofiber work within the LV wall. This difference appears large enough to regard local myocardial function as an important determinant for abnormalities in perfusion, metabolism, structure and pump function during asynchronous electrical activation. Pacing at sites that cause more synchronous activation may limit the occurrence of such derangements.  (+info)

Partial cavotricuspid isthmus block before ablation in patients with typical atrial flutter. (8/664)

OBJECTIVES: The purpose of this study was to prospectively evaluate preexisting partial isthmus block in the context of an electrophysiologically directed linear ablation strategy for typical atrial flutter (AF). BACKGROUND: Double potentials (DPs) separated by an isoelectric interval have been recognized as markers of local block. However, the presence and significance of DPs in the cavotricuspid isthmus during AF before ablation have not been evaluated. METHODS: Thirty consecutive patients with AF (counterclockwise: 24, clockwise: 6) were studied during AF. Sequential withdrawal mapping was performed in the cavotricuspid isthmus from the tricuspid valve (TV) to the inferior vena cava (IVC) edge with electrograms coinciding with the center of the surface electrocardiographic plateau during counterclockwise AF or with the initial downslope of the positive flutter wave during clockwise AF. Atrial electrograms along this line were categorized as double, single or fractionated potentials (SPs or FPs). After demarcation of the zone of contiguous DPs, radiofrequency (RF) catheter ablation was performed during AF only at sites with SPs or FPs (other than DPs) on the mapped line. If isthmus conduction still persisted after AF termination, additional RF applications were delivered using the same electrophysiologic strategy of avoiding DPs with an isoelectric interval during low lateral right atrial pacing for filling in the gap of residual conduction. RESULTS: Before ablation, no DPs were recorded in the isthmus in 19 patients (63%); DPs were recorded only at the IVC edge in five patients, and only at the TV edge in one patient. A contiguous line of DPs extending through more than half the isthmus to the IVC edge was documented in five patients (17%: group DP). In group DP, AF was terminated with 1.4+/-0.5 applications (vs. 5.8+/-3.5 in the remaining patients: p < 0.01). Complete isthmus block was achieved with a total of 3.4+/-0.5 applications (vs. 12+/-6 in the remaining patients: p < 0.01). CONCLUSIONS: Seventeen percent of patients undergoing ablation of AF have preexisting partial isthmus block indicated by a large contiguous zone of DPs separated by an isoelectric interval. Electrophysiologically directed linear ablation avoiding confluent DPs can prevent unnecessary applications for effective cure of AF.  (+info)