In Vivo Ventricular Lesion Growth in Radiofrequency Catheter Ablation

While radiofrequency catheter ablation has proved highly effective in the treafment of various supravenfricular tQchyarrhythmias, resulls in the trentment of ventricular tachycardia invite improvement. Knowledge of lesion growth in vivo might improve understanding of this discrepancy. So far only information from in vitro and in vivo studies using a small 2 mm tip eiectrode is available. Growlh of ventricular radiofrequency lesions created with a 4 mm ahlalion electrode was studied in 11 closed-chest dogs. Endocardia] ablations were performed at 31 left and 35 right ventricuiar sites at a power setting of 25 Watts and 5, 10, 20, 30 or 60 seconds pulse duration. Macroscopic and histopathologic lesion examination were performed after one week survival. Mean lesion volume increased from 52 mm³ after 5 seconds pulse duration to a maximum 388 mm³ and approximately 7 mm depth after 30 seconds. Lesions were prolate spheroid in form, with a sparing of subendocardial myocardium and maximum lesion diameter at some millimeters depth. Results indicate that catheter positioning at no more tlian 7 mm from the target is required for successful ablation. Due to lesion geometry, subendocardial targets demand even more exact catheter positioning, while subepicardial substrates may not be ammenable to ablation if ventricular wall thickness exceeds 7 mm at the ablation site. Repeated pulses at adjacent sites may be required for ablation of extended arrhytbmogenic areas. Volume at 5 seconds was only approximately 15% of mature lesions. Therefore, the use of a short'test pulse after careful mapping may be useful to pinpoint the most appropriate site for ablation in discrete pathways.     

Clinical Observations with a Dual Sensor Rate Adaptive Single Chamber Pacemaker

The Topaz model 515 (Vitatron B.V.) is a dual sensor rate responsive pacemaker for single chamber stimulation. It can be driven by activity counts (ACT) and QT interval measurements. Inappropriate rate modulation due to one sensor can be corrected by "sensor cross-checking." It was implanted in ten patients (20-86 years) of whom seven had complete heart block and atrial arrhythmias. After implantation T-wave amplitude ranged from 0.9mV-3.5 mV. T-wave sensing ranged from 88%–99% in 9/10 patients at the follow-up of 3 weeks. Eight patients remained in default setting of the activity threshold, after evaluation with a short walking test. An exercise test was performed on all patients. In one test, QT sensing was marginal because of lead implantation in the right ventricular outflow tract. Therefore, this pacing rate was only modulated by ACT sensing. All others were tested with equal contribution of information from both sensors (ACT = QT). In 7/9, rate response was satisfactory. When the treadmill was repeated with ACT in five of these seven patients, rate generally accelerated too fast. In one patient the setting was adjusted to "QT > ACT," because of inappropriate acceleration due to activity sensing, in another it was adjusted to "QT < ACT" because of delayed response to activity. The pacing rate and the ACT during treadmill tests in "QT = ACT" mode were more closely correlated in the first 3 minutes, compared with the last 3 minutes. We feel that rate modulation with this new pacemaker is adequate. Sensor blending and sensor cross-checking are of clinical importance.     

Survival after a first episode of spontaneous bacterial peritonitis. Prognosis of potential candidates for orthotopic liver transplantation

Abstract To determine the potential role of orthotopic liver transplantation (OLT) in cirrhotic patients surviving a first episode of spontaneous bacterial peritonitis (SBP), medical records of 79 patients presenting with a first episode of SBP were reviewed. Of these patients, 37 were selected as potential candidates for OLT using the following criteria: absence of hepatocellular carcinoma; no severe organ failure other than the liver; age ≤ 66 years; and survival after SBP > 60 days. Survival time was calculated from the day of SBP diagnosis. Prognostic value of clinical, biological and bacteriological data recorded at the time of SBP was determined using univariate and multivariate analysis (Cox's regression model).
Survival rate of the potential candidates for OLT at 3 months, 1 year and 2 years was 94, 46 and 30%, respectively. Serum creatinine value ( P = 0.001) and Pugh score ( P = 0.005) were independently correlated with death. The 1 year survival rate was 80% for the 11 patients with a Pugh score < 10, and 26% for the 26 patients with a Pugh score ≥ 10.
Our results suggest that after SBP, OLT should be considered in patients with severe liver disease. Survival of patients with a moderate liver disease (i.e. Pugh score < 10) might be relatively high.     

Abnormal Automaticity as Mechanism of Atrial Tachycardia in the Human Heart—Electrophysiologic and Histologic Correlation:

Abnormal Automaticity in Human Atrium, introduction: A 32-year-old woman was operated upon because of drug refractory atrial tachycardia.
Methods and Results: Electrophysiologic study was performed prior to operation. During surgery, epicardial mapping of the electrical activity of the left atrium was performed. The left atrial appendage was resected and studied in a tissue bath. Thereafter, histologic examination was performed. Polarity of the P wave in the surface ECG suggested that the tachycardia originated high in the left atrium. Epicardial mapping disclosed earliest activation in the apex of the left atrial appendage. Intracellular recordings from surgical specimen made at the site of origin, which was marked during surgery, revealed cells with phase 4 depolarization at cycle lengths ranging from 360 to 540 msec. Exit block prevented spread of activation from the spontaneously firing cells to surrounding tissue. Histology showed that spontaneous activity arose in an area with abnormal cells-characterized by an amorphous, pale eosinophilic staining cytoplasm and absence of nuclei-surrounded by normal myocytes.
Conclusion: The observations indicate that the mechanism of the atrial tachycardia was based on abnormal automaticity in an area consisting of a conglomeration of normal and abnormal myocytes.     

Two-to-One AV Block Associated with the Congenital Long QT Syndrome

2:1 AV Block in LQTS. Introduction Conduction abnormalities associated with long QT syndrome (LQTS) have been reported as "pseudo 2:1 AV block" due to sinus intervals shorter than ventricular refractoriness.
Method and Results: We report the electrophysiologic characteristics of a patient suffering from congenital LQTS with episodes of true 2:1 AV block. Induction of 2:1 infra-Hisian blocks and return to 1:1 conduction were observed using single atrial and ventricular extrastimuli. The block was located in the Purkinje network but not in the myocardium.
Conclusion: The His-Purkinje system of our LQTS patient displayed dynamic properties with a strong increase in refractoriness for short-long sequences and a decrease for long-short sequences that triggered intermittent 2:1 AV blocks.     

Gender Differences in Patients Referred for Atrial Fibrillation Management to a Tertiary Center

Background: Atrial fibrillation (AF) ablation is less frequently performed in women than in men. Although the prevalence of AF is slightly higher in men, this does not fully account for the lower number of AF ablations performed in women. This study sought to examine the effect of gender on referral for AF and subsequent AF management.
Methods: Consecutive patients referred to our tertiary arrhythmia outpatient clinic for AF management were retrospectively analyzed.
Results: Of 264 patients referred, only 27% were women. Women were older than men (63 ± 9 vs 58 ± 11 years, P = 0.002), more often had paroxysmal AF (78% vs 63% in men, P = 0.022), and women more frequently complained about palpitations (71% vs 49%, P = 0.002). In addition, they had more often experienced amiodarone side effects than men (56% vs 36%, P = 0.046). In this referred population, there was no difference in the proportion of women and men undergoing AF ablation immediately following the initial evaluation (21% vs 25%, P = ns), at any time during the follow-up (38% vs 44%, P = ns), and there was no difference in the proportion of patients undergoing atrioventricular node ablation in both sexes (6% of women vs 3% of men, P = ns).
Conclusions: There is an important difference in the proportion of men and women referred for management of AF in a specialized outpatient arrhythmia clinic, with women being referred three times less often than men. However, there is no gender-related difference in the subsequent treatment decisions. These findings emphasize the importance of focusing on management of symptomatic AF in women.     

Procedures associated with infective endocarditis in adults: A case confrol study

OBJECT: To assess the relative risk of infective endocarditis associatedwith various procedures and the protective efficacy of antibioticprophylaxis by a case-control study. BACKGROUND: Recommendations for the prevention of infective endocarditisare based on the hypothesis of a relationship between proceduresand infective endocarditis which is supported by anecdotal reportsand data from experimental models. METHODS: Cases met the Von Reyn's diagnostic criteria modified with echocardiographicand macroscopic findings, Controls were recruited from cardiologyor medicinal wards. Cases (n=171) and controls were matchedas regards sex, age and underlying cardiac condition, They wererequested to indicate all the medical, surgical or dental procedureswithin the previous 3 months, Among potential confounding factors,infectious episodes and skin wounds in the previous 3 monthswere reported, Antibiotic prophylaxis administration was documentedfor type, dosage, duration and administration schedule. RESULTS: Cases significantly more frequently than controls had undergoneat least one procedure (matched odds ratio, 1.6; 95% confidenceinterval, 1.01 to 2.53). Dental procedures considered as a wholewere not associated with an increased risk, although scalingand root canal treatment showed a trend towards a higher riskof infective endocarditis (P=0.065). Among non-dental procedures,only surgery appeared to be at risk (matched odds ratio, 4.7;95% confidence interval, 1.02 to 22). Considering all procedures,the risk of infective endocarditis increased significantly withthe number of procedures. While general co-morbid conditionsdid not differ between the two groups, cases significantly morefrequently than controls had experienced an infectious episodeor a skin wound In multivariate analysis, only infectious episodesand skin wounds significantly increased the risk of infectiveendocarditis. Scaling was the only independent risk factor forviridans streptococcal infective endocarditis. The 46% protectiveefficacy of antibiotic prophylaxis was not significant. CONCLUSIONS: Procedures do increase the risk of infective endocarditis. Theinterpretation of the apparent low risk associated with dentalprocedures may be as a result of the current practice of antibioticprophylaxis. Our data suggest that surgery should be more clearlymentioned in future guidelines, and reemphasize that a rigoroustreatment of any focal infection in cardiac patients is mandatory.From the efficacy rate of antibiotic prophylaxis, it can beestimated that the overall incidence of infective endocarditismight be reduced by 5 to 10% in France by appropriate use ofantibiotic prophylaxis in cardiac patients.