Long-term Prevention of Vagal Atrial Arrhythmias by Atrial Pacing at 90/Minute: Experience with 6 Cases

Six patients (5 men, 1 woman) with a history ranging from 3–16 years of resistant vagal atrial arrhythmias were treated by atrial pacing at a rate of 90Jmin. These patients have been followed up for an average of 5.5 years (range 2–11 years) with favorable resutls. The arrhythmias were charactemed by daily or weekly attacks of rypical alrial flutter and atrial fibrillalion occurring mainly or exclusively at night, at rest, or in the digestive periods in otherwise normal hearts of middle-aged palients (first attack between 25 and 54, mean 40). The arrhythmias werc resistant to quinidinc, and were usually aggravated by digitalis, beta-blockers and verapamil. Amiodaroneisusually the only effective drug in this syndrome, but was not used before pacing in the 2 first cases, and was in effective in the other 4 cases. Electrophysiologic studies confirmed the absence of sick sinus syndrome, and the close relationship betwecn a relative bradycardia and the onset of the arrhythmia. Atrial pacing alone totally controiled the arrhythmia in 1 palient; amiodarone was used in conjunction with pacing in 3 palients. In 1 patient the improvement was clear but incomplete, and in 1 patient permanent alrial fibrillation occurred shortly afler pacemaker implantalion.     

Incidence and Prevention of Cardiac Tamponade Complicating Ablation for Atrial Fibrillation

Cardiac tamponade complicating catheter ablation of atrial fibrillation (AF) occurs in approximately 1% of pulmonary vein isolation (PVI), and up to 6% of linear ablation procedures. We reviewed 348 consecutive AF ablation (including repeat) procedures over 1 year, which all included PVI, with additional linear lesions at the mitral isthmus in 73%, and cavotricuspid isthmus (CTI) in 76%. An irrigated-tip ablation catheter was used, with power limited to 25–35 W for PVI and 45–60 W for linear lesions. Tamponade occurred in seven men and three women (2.9% of the population) during the creation of linear ablation lesions. Mechanical perforations occurred in two patients, and "popping" during radiofrequency (RF) energy delivery at the mitral isthmus in six, and at the CTI in two patients. Peak RF power was significantly higher in patients with than without tamponade (53 ± 4 W vs 48 ± 7 W; P = 0.02), and was greater than 48 W in all cases of "popping." In the following year, RF power for linear ablation was limited to ≤42 W. Among 398 procedures, tamponade occurred in four patients (1.0%; P = 0.047 vs first year), three from "popping" and one from mechanical trauma. Procedural success rate remained the same despite reduction of power. Risk of tamponade was highest during linear ablation, mainly associated with high energy delivery and "popping." Reducing the energy limited, though did not eliminate this complication.     

Blood Coagulation Factors in Total Body Irradiation

Investigation of the clotting factors in five humans accidentally exposed tototal body irradiation disclosed no deficiencies. There was no evidence of acirculating anticoagulant in any case. Moderate fibrinolysis was seen in twoinstances in the same individual but was not evident in the others. At theeleventh day there was uniformly a moderate increase in the levels of fibrinogen. At the twenty-ninth day there was observed an increase in the levels offactors V and VIII coincidental with thrombocytopenia. This change reverseditself with recovery. A similar increase in the levels of factor VIII and less soof factor V was seen in cases of idiopathic thrombocytopenic purpura andsecondary thrombocytopenia. An increase in level of factor VIII was observedin patients on oral coumarin anticoagulation. It is concluded that the supernormal levels of factors V and VIII are secondary to lowered thrombin levelsin the circulating plasma as a result of the thrombocytopenia and not duedirectly to the effect of irradiation.

Submitted on June 12, 1961 Accepted on September 15, 1961     

Sino-Atrial Dissociation: Evidence by Intracardiac Recordings in Man and by Microelectrode Studies on Isolated Rabbit Atrium

The electrophysiologic mechanisms of sinus dysfunction have recently been determined by direct recordings of the sinus node electrogram. The association of various degrees of abnormalities in the formation of the impulse within the sinus node and of sinoatrial conduction block, represents the pathophysiological substrate of the mechanism of sinus node dysfunction. The purpose of this work is to present clinical and experimental data supporting the concept of sinus node isolation. In our clinical case, the sinus node was probably intact despite aspects of sinus node dysfunction on the surface ECG. Sinus node electrograms were recorded with a sinoatrial conduction time of 100 ms (normal values in our laboratory: 83 ms +/- 38 ms). Atrial mapping demonstrated that the area depolarized by the sinus node involved a 2 cm2 zone surrounding it. This perisinusal activity could not be recorded on the surface ECG. Both exit and entry blocks in the sinus node were demonstrated. Our experimental data showed a total desynchronization between the electrical activity of the sinus node and that of the atrium under hypoxic conditions. Both types of cases demonstrated that an atrial dysrhythmia was coexisting with regular sinus activity. From these data we concluded that a sinus node free from any pathological involvement could be associated with severe symptoms of sinus node dysfunction on the surface ECG.     

MALE PSEUDOHERMAPHRODITISM WITH HYPERTENSION DUE TO A 17α-HYDROXYLATION DEFICIENCY

A case of male pseudohermaphroditism aged 48 years with systemic hypertension and hypokalaemic alkalosis is described. Results of metabolic studies point to a 17alpha-hydroxylase deficiency demonstrated by low cortisol (0-56 mg/24 h), high corticosterone (270 mg/24 h) and 11-deoxycorticosterone (5 mg/24 h) secretion rates. Adrenocorticotrophin and gonadotrophin levels were markedly raised but plasma androstenedione (3 ng/dl), testosterone (17 ng/dl), oestrone (3 ng/dl) and oestradiol(1-8 ng/dl) were all low. Plasma aldosterone levels and secretion rates in urine were low and were surprisingly unaffected by dexamethasone therapy although low renin levels rose with a marked return of the erect posture effect. Therapeutic levels of dexamethasone were, however, followed by incipient renal failure.     

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.     

Specific Electrocardiographic Features of Manifest Coronary Vein Posteroseptal Accessory Pathways

Coronary Vein Accessory Pathways. Introduction: Some posteroseptal accessory pathways (APs) can be successfully ablated by radiofrequency current only from inside the coronary sinus (CS) or its branches, because of an absolute or relatively epicardial location. The aim of this study was to identify ECG features of manifest posteroseptal APs requiring ablation in the CS or the middle cardiac veins (MCVs). Methods and Results: One hundred seventeen consecutive patients with manifest posteroseptal APs successfully ablated: (1) ≥ 1 cm deep inside the MCV (group MCV: n = 13); (2) inside the CS, including the area adjacent to the MCV ostium (group CS: n = 10); (3) at the right (group R: n = 60); or (4) the left posteroseptal endocardial region (group L: n = 34) were included. We reviewed delta wave polarity (initial 40 msec) and QRS morphology during sinus rhythm and atrial pacing as well as electrogram characteristics in these patients. The local target site electrogram in groups MCV and CS was characterized by a longer atrial to ventricular electrogram interval, suggesting a longer course of the pathway and more frequent recording of a presumptive AP potential compared to the group ablated at the right or left endocardium. The most sensitive ECG feature for group CS or group MCV was a negative delta wave in lead II in sinus rhythm (87%), but specificity (79%) and positive predictive value (50%) were relatively low. A steep positive delta wave in aVR during maximal preexcitation possessed the highest specificity and positive predictive value (98% and 88%, sensitivity 61%) which increased to 99% and 91%, respectively, when combined with a deep S wave in V₆ (R wave ≤ S wave). Conclusion: These data suggest that posteroseptal APs ablated inside the coronary venous system have highly specific features, including the combination of a steep positive delta wave in lead aVR and a deep S wave in lead V₆ (R wave ≤ S wave) during maximal preexcitation. The highest sensitivity is provided by a negative delta wave in lead II. These findings may be helpful for anticipating and planning an epicardial ablation strategy.     

Circadian Variations in Minute Ventilation Can Be Reproduced by a Pacemaker Sensor

Special software allowing the memorization of 24-hour minute ventilation can be loaded into the memoiy of the Chorus RM, a DDDR pacemaker driven by minute ventilation. This feature was tested in the postimplant period in 13 patients. Measurements of minute ventiiation, respiratory rate, and respiratory amplitude were analyzed according to prospectively defined diurnal and nocturnal time periods. Minute ventilation decreased by 39% (P < 0.001) from the diurnal to the nocturnal phase, while respiratory rate and amplitude decreased by 18% and 28%, respectively (P < 0.001 each). Thus, minute ventilation allowed discrimination between sleep and waking hours. This information could be utilized to modulate the backup rate of the pacemaker.