Right Bundle Branch Block of Unknown Age in the Setting of Acute Anterior Myocardial Infarction: An Attempt to Define Who Should Be Paced Prophylactically

It is widely accepted that patients presenting with acute anterior myocardial infarction and acute onset of right bundle branch block should be prophylactically paced in contrast with those who have a chronic bundle branch block. The admitting physician is faced with the dilemma of how to act if the age of this conduction disturbance is unknown. This problem has further intensified in recent years, with the introduction of thrombolytic treatment, where insertion of a central vascular line is associated with increased morbidity. The objectives of this study were to define clinical or electrocardiographic parameters that may help the admitting physician to decide whether patients presenting with an anterior wall myocardial infarction and a right bundle branch block of unknown age should be prophylactically paced. We examined prospectively the in-hospital clinical course of 39 consecutive patients presenting with an acute myocardial infarction in whom the age of a right bundle branch block upon admission was unknown (group C, n = 39) and compared it with two similar groups of patients who presented with an acute right bundle branch block (group A, n = 38) and with a known chronic right bundle branch block (group B, n = 22). Thirty-three patients (33%) died, with cardiogenic shock being the leading cause of death in the entire population. Prophylactic pacing, which was carried out in 66% and 54% of patients in groups A and C, respectively, did not reduce mortality rates. No clinical or electrocardiographic variables on admission were predictive to support prophylactic pacing in group C. In 10 of 46 (22%) patients who were prophylactically paced with a transvenous electrode, the following complications attributed to the procedure were detected: (1) either rapid sustained ventricular tachycardia (during implantation) that was unresponsive to overdrive pacing, or ventricular fibrillation necessitating electrical defibrillation (4 patients); (2) recurrent episodes of rapid nonsustained ventricular tachycardia, which stopped only after the pacemaker was turned off (1 patient); (3) complete AV block (1 patient); (4) fever appearing on the third or fourth day after implantation (3 patients); and (4) a large hematoma in the groin in 1 patient who was treated with thrombolysis shortly before pacemaker electrode insertion. Thus, the complications of transvenous temporary pacing in the era of thrombolysis may outweigh any theoretical advantage. (PACE 1995; 18:1496-1508)     

PLASMA GLUCAGON RESPONSE TO ARGININE INFUSION IN CHILDREN AND ADOLESCENTS WITH DIABETES MELLITUS

Plasma glucagon response to an arginine infusion was studied in children and adolescents belonging to the following groups: (I) twenty-two controls; (II) six subjects with delayed insulin peak during oral GTT; (III) ten diabetics on diet and/or oral therapy; (IV) six newly diagnosed uncompensated diabetics; and (V) eight diabetics on insulin therapy. The fasting glucagon concentrations and rise of glucagon in response to arginine in the patients of Groups II, III and V were similar to those of the controls (Group I). The basal levels and rise of glucagon in the newly diagnosed, uncompensated dibetic children (Group IV) was elevated compared to the other groups but the difference was statistically not significant. The results of this investigation favour the hypothesis that the hyperglucagonaemia in diabetes is a secondary effect to the metabolic derangement, bearing a direct relationship to the degree of homeostastic decompensation.     

Unipolar and Bipolar Electrogram Characteristics Predict Exit Block during Pulmonary Vein Antral Isolation

Introduction: The usefulness of unipolar electrograms (EGMs) has been reported in assessing lesion transmurality and conduction block along ablation lines. It is unknown whether unipolar and bipolar EGM characteristics predict exit block during pulmonary vein isolation (PVI) procedures. Methods and Results: Twenty patients (63 ± 7 years; 14 males [70%]) undergoing PVI with a circular mapping catheter (CMC) placed outside each PV ostium were retrospectively studied. After entrance block was achieved, pacing at each bipole around the CMC was performed to assess for absence of atrial capture (exit block). Bipolar EGMs recorded before pacing were examined for voltage, duration, fractionation, and monophasic morphology. Unipolar EGMs were examined for positive and negative amplitude, PQ segment elevation, fractionation, and monophasic morphology. The association of these parameters with atrial capture (absence of exit block) at each site was analyzed. After achievement of entrance block, only 23 of 64 PV antra (36%) exhibited exit block. Unipolar EGMs at sites with persistent capture were more likely to be fractionated and had larger negative deflections. Bipolar EGMs at sites with persistent capture showed higher amplitude, longer duration, were more likely to be fractionated, and were less likely to be monophasic. In a multivariate logistic regression model, bipolar and unipolar fractionation, bipolar duration, and lack of bipolar monophasic morphology were independently associated with persistent atrial capture. Conclusion: Specific unipolar and bipolar EGM characteristics are associated with left atrium capture after PV antral isolation. These parameters might be useful in predicting the need for further ablation to achieve exit block. (PACE 2012; 35:1294–1301)     

Short-Term Thrombosis after Transvenous Permanent Pacemaker Insertion

In order to assess prospectively the incidence and significance of venous thrombosis early after permanent transvenous pacemaker implantation venographic studies were carried out in 40 consecutive patients. The venograms performed between 1 and 6 months (mean 4 months) after the implantation were normal in 31 patients (77%), in six patients (15%) they showed partial venous obstruction and in three patients (8%) total obstruction. Between 6 and 12 months (mean 9 months) the venograms of five patients, that were previously normal, showed partial venous thrombosis. No changes were found in the venograms performed later. Only two of 14 patients with thrombosis of the great veins was clinically symptomatic and developed arm edema, that resolved spontaneously within about a month. No difference in incidence of abnormal venograms was found according to the type of insulation, the polarity of the electrode and the route of entry.     

Supraclavicular Vein Approach for Upgrading an Implantable Cardioverter Defibrillator to a Biventricular Device

Total occlusion of the left subclavian vein was found in a 52‐year‐old patient, 5 years after implantation of an implantable cardioverter defibrillator (ICD). During replacement, the ICD was upgraded to a biventricular device for worsening of the patient's congestive heart failure to New York Heart Association class III. Insertion of the left ventricular lead in the ipsilateral vein system was successfully achieved by using the supraclavicular approach, enabling puncturing of the left subclavian vein medially to the obstruction. (PACE 2010; 634–636)