Prem K. Gupta

Hypomagnesemia and refractory cardiac arrhythmia in a nondigitalized patient

Abstract A case of hypomagnesemia and refractory cardiac arrhythmia is presented. The patient had no evidence of clinical heart disease and was not receiving digitalis therapy. The cardiac arrhythmia was refractory to all usual forms of therapy but was instantly abolished with intravenous magnesium therapy. The unusual nature of this relation and a possible hypothesis to explain its occurrence are discussed.

Appraisal of sinus nodal recovery time in patients with sick sinus syndrome.

Abstract Right atrial pacing for 2 to 5 minutes at rates ranging from 90 to 150/ min was performed in 17 patients with the sick sinus syndrome and in 15 control subjects with no evidence of sinus node disease. The postpacing pause or the sinus recovery time was defined as the pause between the last paced atrial beat and the subsequent sinus escape beat. The corrected sinus recovery time was determined by subtracting the basic sinus cycle length from the sinus recovery time. In the 15 control subjects, the corrected sinus recovery time ranged from 0 to 375 msec (210 ± 131 [mean ± standard deviation]). In patients with the sick sinus syndrome, the corrected sinus recovery time was normal in 11 (−150 to 350 msec) and prolonged in 6 (480 to 5,690 msec). Intravenously administered atropine (0.6 to 2 mg) used in 11 patients produced an adequate increase in the sinus rate in 6 patients. Junctional escape rhythm lasting for several seconds appeared in three of seven patients who underwent repeat atrial pacing after administration of atropine. Two of these had a normal control recovery time and an adequate response of the sinus rate to atropine administration; in one, the control recovery time was slightly prolonged and the response to atropine was inadequate. In the remaining four patients, three with a normal and one with a prolonged control recovery time, no significant change in recovery time occurred after administration of the drug. We conclude that only a limited number of patients with the sick sinus syndrome have an abnormal corrected sinus recovery time. Some patients with a normal control recovery time may show an abnormal response when atrial pacing is repeated after atropine administration.

Lidocaine-induced heart block in patients with bundle branch block

Abstract His bundle electrography and atrial pacing were used to evaluate the effect on cardiac conduction of an intravenous bolus injection (50 to 100 mg) of lidocaine in 21 patients with various intraventricular conduction abnormalities and ventricular premature beats. Sixteen patients (76 percent) had prolonged His-Purkinje conduction time (H-V interval greater than 55 msec). Six patients (all with a prolonged H-V interval) had earlier shown transient second degree or complete heart block. Administration of lidocaine produced complete heart block distal to the His bundle potential in two patients. Both patients had a prolonged H-V interval (100 and 140 msec, respectively) and had shown 2:1 A-V block distal to the H deflection on atrial pacing before the injection. A third patient, with an H-V interval of 70 msec, showed second degree block distal to the H deflection during atrial pacing after administration of lidocaine but not before. An additional patient, observed clinically to have alternating right and left bundle branch block, experienced cardiac standstill after the injection. Lidocaine should be used cautiously in patients with incomplete bilateral bundle branch block, and a temporary pacemaker should be considered in patients with a prolonged H-V interval or known trifascicular disease.

Pericarditis complicating acute myocardial infarction: Incidence of complications and significance of electrocardiogram on admission

Abstract The records of 31 patients with pericarditis complicating acute myocardial infarction were reviewed and compared to a control group of 274 patients with infarction but without pericarditis. The cases of pericarditis all occurred within one week of myocardial infarction and were included only if a typical pericardial friction rub was heard by more than one observer. Sex distribution and age were similar in both groups. There was a higher incidence of anterior wall infarction in the group with pericarditis. The incidence of atrial arrhythmias was less than in controls, while the incidence of ventricular arrhythmias, significant congestive heart failure, and death was slightly greater in those with pericarditis. Maximum ST segment elevation on the day of admission in the group with pericarditis was compared with a control group. In those with anterior wall infarction and pericarditis, the average ST segment elevation in the anterior precordium was 5.6 mm. compared to 2.6 mm. in the controls. In those with inferior wall infarction and pericarditis, the average ST segment elevation was 3.6 mm. in Lead III compared to 1.7 mm. in a control group. It is concluded that patients who develop pericarditis within one week of acute myocardial infarction do not have an increased incidence of atrial arrhythmias. The incidence of ventricular arrhythmias, significant congestive heart failure, and death are slightly greater and may be due to more extensive myocardial infarction. The higher initial ST segment elevation in patients with pericarditis may indicate a greater amount of injury or may be a sign of pericardial involvement that is seen before clinical pericarditis is present.

Atrioventricular block with lidocaine therapy

Abstract A case is presented of complete atrioventricular (A-V) block occurring after a 50 mg bolus injection of lidocaine. Base-line studies before administration of lidocaine showed evidence of trifascicular block manifested by complete right bundle branch block, left anterior hemiblock and a markedly prolonged H-V interval. Advanced A-V block and then complete A-V block distal to the His bundle developed after administration of lidocaine. Lidocaine should be used with caution in patients with trifascicular disease; if it is administered to such patients, insertion of a temporary pacemaker catheter should be considered.

Intraventricular Conduction Time (H-V Interval) During Antegrade Conduction in Patients with Heart Block

Intraventricular conduction time (H-V interval) was recorded during antegrade conduction in 16 patients with various intraventricular conduction abnormalities who showed second degree or complete heart block. In 9 patients the block was localized distal to the His bundle potential (H) by His bundle electrography. The remaining 7 patients had shown block before the study. The H-V interval during antegrade conduction was prolonged in 15. Atrial pacing was performed in 6 patients during 1:1 A-V conduction. In 3 patients second degree atrioventricular (A-V) block developed distal to the H potential. In 2 of these patients, complete heart block had been noted earlier, and in 1 it developed 3 months after the study. The remaining 3 patients showed 1:1 A-V conduction during atrial pacing, even though each had earlier shown complete heart block. We conclude that the majority of patients with bundle branch block who experience heart block have a prolonged H-V interval during antegrade conduction. Atrial pacing performed during 1:1 A-V conduction may or may not produce block distal to the H potential.

Continuous Holter monitoring of patients with bifascicular block complicating anterior wall myocardial infarction

Abstract Fourteen patients with acute anterior wall myocardial infarction complicated by bifascicular block were studied. In addition to clinical evaluation, all patients had continuous Holter monitoring of their electrocardiogram throughout their hospital course. Seven patients died in the hospital (hospital mortality rate 50 percent). Five of the seven died with cardiogenic shock. In four of these patients the terminal electrocardiographic event was a slow idioventricular rhythm with failure of pacemaker capture and in one, ventricular fibrillation. Primary ventricular fibrillation was the terminal event in only one patient. The seventh patient died on the 25th day with sudden complete heart block. Review of the Holter tapes of the 14 patients revealed episodes of the following arrhythmias: complete heart block in three patients (21 percent), atrial fibrillation in two, accelerated ventricular rhythm in two, fast ventricular tachycardia in two and ventricular fibrillation in one. All patients had ventricular premature beats. We conclude that the incidence of documented primary complete heart block when myocardial infarction is complicated by bifascicular block is large enough to warrant prophylactic temporary pacemaker insertion. Temporary pacing is also of value in treating the frequently observed ventricular arrhythmias.

Complete right bundle branch block with left axis deviation: Significance of vectorcardiographic morphology

Abstract Sixty-five patients with a VCG pattern of complete right bundle branch block and left axis deviation (> −30 degrees) were studied. There were 46 patients with counterclockwise rotation (Group A) and 19 patients with clockwise rotation (Group B) in the horizontal plane. His bundle electrograms were recorded in 24 Group A patients and in four Group B patients. The Group A patients were slightly younger (average age 69 years) than the Group B patients (average age 75 years). The incidence of previous myocardial infarction (Group A 12 46 , Group B 4 19 ) and hypertension (Group A 13 46 , Group B 4 19 ) were similar. Diabetes mellitus was slightly more common in Group B (Group A 7 46 , Group B 5 19 ). Cardiomegaly (Group A 16 46 , Group B 12 19 ) and congestive heart failure (Group A 13 46 , Group B 9 19 ) were more common in Group B. Episodes of syncope (Group A 19 46 , Group B 4 19 ) and prolonged H-Q interval (55 msec. or greater) (Group A 19 24 , Group B 2 4 ) were more frequent in Group A patients. However, in individual cases there was no definite relationship between prolonged H-Q interval and syncope. It is concluded that this pattern represents a wide spectrum of disease and anatomical defects. The relationship of VCG morphology to clinical course does not appear to be close enough to predict the course of an individual patient or aid in clinical management.

Effects of Ventricular Premature Contractions on Atrioventricular Conduction. Studies with His Bundle Electrography

The effect of ventricular premature contractions on atrioventricular (A–V) conduction of the following sinus beat was studied in 25 patients with use of His bundle electrography. Facilitation of A–V conduction (shortening of the A–H interval) in the postextrasystolic beat was observed in 17 patients. This facilitation was believed to be due to a longer recovery period of the A–V node after its premature retrograde (and frequently concealed) depolarization by the ventricular premature contraction. Slowing of A–V conduction (prolongation of the A–H interval) after interpolated or repetitive ventricular premature contractions occurred in five patients. In these instances, after retrograde depolarization by the ventricular premature contraction, the A–V node was still partially refractory and conduction of the postextrasystolic beat was delayed. Retrograde P waves without resetting of the A–V node were documented; in these cases, the interval after the retrograde P wave was fully compensatory, suggesting retrograde and antegrade sinoatrial block.

Right Bundle Branch Block With Periods of Alternating Left Anterior and Left Posterior Hemiblock Clinical Evidence of Incomplete Fascicular Block

The case presented had an electrocardiographic pattern of complete right bundle branch block with alternating periods of left anterior hemiblock and left posterior hemiblock. During one of the periods of alternating hemiblock, an His bundle electrogram was recorded and the His Purkinje (H-V interval) conduction time was within normal limits. In a second episode of alternating hemiblock, periods of Mobitz type II second-degree A-V block were noted. It is postulated that this case provides clinical evidence that incomplete block of a fascicle may occur in spite of an electrocardiographic pattern of complete fascicular block. It is thought that the periods of alternating hemiblock result from a changing relationship between conduction velocity and refractory pe riod.