Simultaneous anterograde fast-slow atrioventricular nodal pathway conduction after procainamide

Three patients with paroxysmal supraventricular tachycardia underwent electrophysiologic studies that included His bundle recordings, incremental atrial and ventricular pacing and extrastimulation before and after intravenous infusion of 500 mg of procainamide. In all three patients the tachycardia was induced during atrial pacing or premature atrial stimulation, or both. Two of the three patients had discontinuous atrioventricular (A-V) nodal curves with induction of a slow-fast tachycardia during failure in anterograde fast pathway conduction and one patient had a smooth A-V nodal curve with induction of a slow-fast tachycardia at critical A-H interval delays. After procainamide: (1) in all three patients atrial pacing induced A-V nodal Wenckebach periodicity (cycle length 300 to 400 ms) resulting in simultaneous anterograde fast and slow pathway conduction (one atrial beat resulting in two QRS complexes) and retrograde fast pathway conduction initiating an echo response or a slow-fast tachycardia, or both; (2) in all three patients there was enhanced conduction and shortening of refractoriness of the anterograde fast pathway and depressed conduction and lengthening of refractoriness of the retrograde fast pathway; and (3) in two patients there was inability to sustain tachycardia because of selective block within the retrograde fast pathway. In conclusion: (1) procainamide altered conduction and refractoriness of the anterograde fast and slow pathways so that simultaneous conduction could occur during atrial pacing, resulting in a double ventricular response and a slow-fast echo or tachycardia, or both; and (2) the differential effects of procainamide on anterograde fast and retrograde fast pathways suggests two functional A-V nodal fast pathways, one for anterograde and the other for retrograde conduction.     

Aortico-right ventricular shunt following aortic valve replacement

A 58-year-old man developed cardiac decompensation following aortic valve replacement as a result of an aortico-right ventricular fistula. Serial hemodynamic and electrocardiographic changes are presented. Attention is drawn to this rare complication as a cause of hemodynamic deterioration following aortic valve surgery.     

Electrocardiographic antecedents of primary ventricular fibrillation. Value of the R-on-T phenomenon in myocardial infarction.

Primary ventricular fibrillation was seen in 20 of 450 consecutive patients (4-4%) admitted within 24 hours after the onset of acute myocardial infarction. Compared with patients without primary ventricular fibrillation they showed a lower mean age group and a higher incidence of anterior infarction. Warning ventricular arrhythmias preceded primary ventricular fibrillation in 58% of cases. However, warning arrhythmias were also present in 55% of patients without primary ventricular fibrillation. The following mechanisms of initiation of primary ventricular fibrillation were seen. 1) In one patient, it was initiated by supraventricular premature beats showing aberrant intraventricular conduction. 2) In 2 patients, ventricular tachycardia degenerated into primary ventricular fibrillation. 3) In 17 patients, it was initiated by a ventricular premature beat; in 10 of these, the premature beat showed early coupling (RR/QT less than 1--the R-on-T phenomenon). However, ventricular premature beats showing the R-on-T phenomenon were also observed in 49% of patients without primary ventricular fibrillation. In 7, primary ventricular fibrillation was initiated by a late-coupled ventricular premature beat (RR/QT greater than 1); in 2, the very late coupling resulted in a ventricular fusion beat. The study suggests that warning arrhythmias and the R-on-T phenomenon are poor predictors of primary ventricular fibrillation in acute myocardial infarction. The observation that 41% of primary ventricular fibrillation was initiated by a late-coupled ventricular premature beat suggests that ventricular vulnerability during acute myocardial infarction may extend throughout most of the cardiac cycle and is not necessarily confined to the QT interval.     

Differential effects of functional autonomic blockade on the variables of sinus nodal automaticity in sick sinus syndrome

To study the pathophysiologic mechanism of sick sinus syndrome and to establish the relation of intrinsic heart rate, corrected sinus nodal recovery time and sinoatrial conduction time in this syndrome, electrophysiologic studies were conducted in 22 men (mean age 60 ± 12 years) with the clinical diagnosis of sick sinus syndrome. Measurements were determined before and after autonomic blockade with propranolol (0.2 mg/kg body weight) and atropine sulfate (0.04 mg/kg). Fifty-nine percent of patients (Group I) had an abnormal intrinsic heart rate, suggesting intrinsic abnormality of sinus nodal automaticity; 41 percent (Group II) had a normal intrinsic heart rate after autonomic blockade, suggesting disturbed autonomic regulation. One patient with an observed intrinsic heart rate higher than the upper limit of predicted intrinsic heart rate was also included in Group II. The mean corrected sinus nodal recovery time before autonomic blockade was 751 ± 502.8 ms and was abnormal (more than 450 ms) in 10 of the 13 patients in Group I and 2 of the 9 patients in Group II. After autonomic blockade this interval was 694 ± 638.7 ms and was abnormal in 12 of the 13 patients in Group I and in 2 of the 9 patients in Group II. The patients in each group could be further classified into three groups on the basis of normal or abnormal corrected sinus nodal recovery time before or after autonomic blockade. Not all patients with abnormal intrinsic heart rate (Group I) had abnormal corrected sinus nodal recovery time and vice versa. Patients in Group II were younger in age, had a lesser incidence of organic heart disease and were more severely symptomatic.Mean sinoatrial conduction time during control studies was 210.4 ±96.3 ms and decreased significantly (143.2 ± 59.6 ms, p < 0.005) after autonomic blockade. This interval was abnormal in 3 of the 13 patients in Group I and in 6 of the 9 patients in Group II during control studies; after autonomic blockade it remained abnormal in 3 patients in Group I and in 1 patient in Group II.It is concluded that determination of heart rate and corrected sinus nodal recovery time after autonomic blockade increases the sensitivity of electrophysiologic testing and offers some insight into the pathophysiology of sick sinus syndrome. Patients with sick sinus syndrome who have a normal intrinsic heart rate have a greater incidence of abnormal sinoatrial conduction time than do those with an abnormal intrinsic heart rate. Thus, abnormal sinoatrial conduction time is usually due to extrinsic autonomic influences.     

Treatment of Renal Colic by Desmopressin Intranasal Spray and Diclofenac Sodium

The vasopressin analogue, 1-desamino-8-arginine vasopressin (desmopressin), is a potent antidiuretic without the pressor effects of vasopressin. A total of 18 patients with acute renal colic due to stone disease received 40 microgram desmopressin intranasal spray with encouraging results. There was a significant decrease in the colic pain intensity from an initial mean visual analogue score of 67 plus/minus 17 mm. to 39 plus/minus 36 mm. within 30 minutes (p less than 0.001). Eight patients (44.4 percent) had complete pain relief within 30 minutes of administering intranasal desmopressin spray. Nine of 10 patients who required intramuscular diclofenac sodium achieved complete pain relief within another 30 minutes. In other words, when intranasal desmopressin spray was administered before diclofenac sodium, 94.4 percent of the patients achieved complete pain relief and were discharged home.The mechanism of analgesic action of desmopressin in renal colic is uncertain. At the peripheral level, desmopressin may alleviate the acute renal colic through its potent antidiuretic effect or by relaxing the renal pelvic and ureteral smooth muscles. The central analgesic effect of desmopressin by stimulating the release of the hypothalamic beta-endorphin is proposed. We conclude that intranasal desmopressin spray can be used successfully in the treatment of renal colic. It may also replace prostaglandin synthetase inhibitors in treating renal colic with the advantage of avoiding the potential side effects. Further studies are needed to investigate whether the combination of desmopressin with analgesics or spasmolytic drugs offers competitive results compared with those achieved by prostaglandin synthetase inhibitors in the treatment of renal colic.     

Antibody to hepatitis B core antigen as a screening test for occult hepatitis B virus infection in Egyptian chronic hepatitis C patients

Purpose  The presence of hepatitis B virus (HBV) DNA in liver tissue and/or in serum in the absence of detectable hepatitis B surface antigen (HBsAg) is called occult HBV infection. This pattern was identified in patients with chronic hepatitis C virus (HCV) infection. The aim of this study was to determine the role of antibodies to hepatitis B core antigen (anti-HBc) as a screening test for occult HBV infection in Egyptian chronic HCV patients. Methods  One hundred chronic HCV patients negative for HBsAg were included and subdivided into two groups according to anti-HBc-IgG seroreactivity. Group A included 71 patients positive for anti-HBc (53 men and 18 women, mean age ± SD 48.8 ± 9.6 years), and group B included 29 patients negative for anti-HBc (18 men and 11 women, mean age ± SD 46.6 ± 11.7 years). All patients were subjected to full clinical assessment, routine laboratory investigations, abdominal ultrasonography and quantification of HBV-DNA by real-time PCR. Results  Chronic HCV patients positive for anti-HBc have more severe liver disease compared with anti-HBc negative patients. Although HBV-DNA in the serum was detected in 22.5% of anti-HBc-positive chronic HCV patients, it was not detected in any of anti-HBc-negative chronic HCV patients. There was no significant difference in any of the clinical and laboratory data tested between anti-HBc-positive patients with and without HBV-DNA in the serum. Conclusion  A significant number of patients with anti-HBc had detectable levels of HBV-DNA in the serum. Egyptian chronic HCV patients have a high prevalence of occult HBV infection.     

The rsR′ pattern in left surface leads in ventricular aneurysm

A characteristic rsR′ pattern or its variants (rSr′ or rSR′) with normal or prolonged QRS duration in left surface leads including the apex lead and the orthogonal scalar X lead was described in 18 patients with coronary heart disease; in 17 of them a ventricular aneurysm was present. Necropsy in 12 patients showed the ventricular aneurysm to be secondary to an extensive confluent scarring of the anterior and antero-lateral portions of the left ventricle. Explanation of the genesis of the electrocardiographic pattern was attempted and its clinical value was suggested.