Simultaneous but separate intermittent and continuous ventricular parasystole

A 19 year old female with end-stage biventricular congestive cardiomyopathy and digitalis toxicity demonstrated double ventricular parasystole with separate but simultaneous intermittent and continuous parasystolic rhythms. The intermittent parasystolic focus, left ventricular in origin, showed failure of entrance block when conducted beats followed its ectopic beats at a critical compensatory interval. Each new parasystolic series was coupled to this interrupting conducted beat at an interval equaling the parasystolic cycle length. Even numbers of conducted beats intervened between ectopic beats during intermittency and odd numbers during uninterrupted parasystole. The mechanism of intermittency was explained by a concealed ventricular tachycardia with 3 3n1 exit block with the demonstration of occasional 3 3n2 Wenckebach exit block within a parasystolic interectopic interval.A second continuous parasystolic rhythm, right ventricular in origin, occurred at a later time without altering the first intermittent parasystolic rhythm.A 4% parallel and proportionate lengthening of both the sinus node and intermittent parasystolic cycle lengths was shown at an even later time.     

Intermittent parasystole with concealed bigeminy

A case is reported of ventricular extrasystolic rhythm showing the features of concealed ventricular bigeminy, and intermittent ventricular parasystolic rhythm, both arising from the same ectopic ventricular focus.     

Parasystole simulating ventricular bigeminy with Wenckebach-type coupling prolongation

A 65-year old male originally presented with repetitive ventricular bigeminal sequences demonstrating progressive prolongation of successive coupling intervals suggesting Wenckeback-type exit block. An even number distribution of conducted beats always intervened between bigeminal sequences. Subsequent analysis proved this to be a fortuitous "pseudo-Wenckebach" phenomenon, with the actual mechanism being continuous parasystole. Additional recording verified a parasystolic rhythm.     

A subvariant of concealed bigeminy.

A subvariant of the "even variant" of concealed bigeminy was studied in two patients. The typical pattern consisted of two types of sequences of conducted sinus beats between extrasystoles. One pattern was bigeminal, i.e., alternating sinus beats and extrasystoles. Between bigeminal sequences were intervals in which there were more than one conducted sinus beat between extrasystoles. In such longer sequences, the numbers of sinus beats were almost invariably even. In the bigeminal sequences, the coupling intervals progressively diminished for each successive extrasystole in the sequence. The proposed explanation for the subvariant was based on a reentry loop in which there were three sites of block: proximal, intermediate, and distal. Block was postulated to take place at the proximal site after those extrasystoles with the shortest coupling intervals, at the intermediate site after odd-numbered conducted sinus beats in the non-bigeminal sequences, and at the distal site ("concealment") after the even-numbered sinus beats in these longer sequences.     

Acute myocardial infarction and ischemic injury during surgery for coronary artery disease.

The incidence of myocardial infarction, acute ischemic injury, and associated serum enzyme abnormalities has been evaluated in four operations involving the coronary circulation. The highest incidence of infarction was associated with internal mammary implantation (Vineberg procedure). There was no significant difference in the incidence of infarction, ischemic injury, or abnormal enzyme levels between patients with stable angina and those with unstable angina who had vein bypass surgery. In operations involving combined vein bypass grafting and valve replacement surgery, the incidence of abnormal serum enzyme elevations was higher than in any other procedure. The incidence of infarction and acute ischemic injury in combined operations was similar to that in other procedures but this may have been due to the difficulty in the ECG diagnosis of infarction in this group of patients, most of whom had abnormal preoperative ECGs.     

The significance of bundle branch block during acute myocardial infarction.

Analysis of the course of 71 patients with acute myocardial infarction complicated by bundle branch block (BBB) confirms a high incidence of atrioventricular (A-V) block (42 per cent) and severe pump failure (35 per cent) in these patients. Hospital mortality was not correlated with BBB per se, but rather with the associated development of second or third degree A-V block (57 per cent with A-V block vs. 12 per cent without A-V block; p less than .0005) or severe pump failure (35 per cent with vs. 11 per cent without severe pump failure; p less than .001). However, late mortality was high and not significantly different among those surviving hospitalization whether transient A-V block was present or absent. Eight of 11 late deaths were sudden. Temporary pacing could not be shown to alter hospital survival statistically, but made the onset of complete heart block a hemodynamically smooth and clinically undetectable event in several patients who later survived. The place of permanent pacing in these patients cannot be clearly determined on the basis of this study or in the available literature. More data obtained either by pooling the experience of several centers or from a prospective randomized study are needed to determine the indications for permanent pacemakers.     

Unifocal origin of multiform extrasystoles in concealed bigeminy

A case of concealed bigeminy is presented in which two forms of extrasystolic complexes were evident on the ECG. One form (type B) appeared after a single conducted sinus beat, in a pattern of manifest bigeminy. The other form (type A) occurred after a sequence of more than one conducted sinus beat. The two configurations have previously been explained on the basis of different foci and mechanisms. Certain features of the ECG from our patient suggested that the two forms originated from a common site. An experimental model was developed in which the right ventricle of a dog was stimulated at sub- or suprathreshold voltages on alternate sinus beats to simulate concealed bigeminy. The ECG obtained during stimulation of a single site was remarkably similar to that recorded from the patient. We have proposed that the extrasystoles that occur after a compensatory pause may spread in a manner different from those that follow a basic cardiac cycle length. The different pattern of propagation is probably ascribable to the lengthening of the refractory period of the cardiac tissues by the compensatory pause.     

Regional and global left ventricular function during intra-aortic balloon counterpulsation in patients with acute myocardial infarction shock

We evaluated the improvement in hemodynamic and left ventricular (LV) function in 15 patients with acute myocardial infarction and cardiogenic shock, who were treated with intraaortic balloon counterpulsation (IABP). They were studied by flow-directed right heart catheterization and nuclear angiography. IABP decreased LV end-diastolic volume from 134 to 114 ml and LV end-systolic volume from 100 to 72 ml. LV stroke volume increased from 34 to 42 ml and cardiac output from 3.0 to 3.6 L/min. Global LV ejection fraction increased from 27.6% to 36.1%, and this was due to improvement in regional ejection fraction in ischemic areas. Pulmonary capillary wedge pressure and pulmonary blood volume decreased. Right ventricular ejection fraction also increased significantly. IABP improved LV function in acute myocardial infarction.     

Comparison of ventricular parasystole with other dysrhythmias after acute myocardial infarction

Three hundred and sixty-nine patients suffering from a recent myocardial infarction were studied over a period of 16 months in a coronary-care unit. Particular attention was paid to ventricular arrhythmias and especially ventricular parasystole. Ventricular parasystole was found in 4 per cent of the patients, identification being helped by the recording of long strips of ECG at slow speed when ventricular ectopic activity was noted.The study has shown that ventricular parasystolic rhythms after acute myocardial infarction are probably benign in contrast to most other ventricular arrhythmias which are associated with an increased mortality.     

Prognosis of left anterior hemiblock in acute myocardial infarction

Four of 32 patients with left anterior hemiblock and an acute anterior wall myocardial infarction died. Left anterior hemiblock was present on admission in 24 patients, and subsequently appeared in 8. Of the 28 survivors, 21 are still alive an average of 2.8 years after the acute myocardial infarction.     

Rate dependent variation in concealed bigeminy

A 63 year old man with angina pectoris was found to have frequent extrasystoles separated by odd as well as even numbers of conducted sinus beats. Analysis of 935 conducted sinus beats showed that premature ventricular beats without interpolation were separated by odd numbers of conducted sinus beats in 117 sequences and even numbers (exceptions) in 48 sequences (p less than 2 X 10(-4)). Tabulation of cycle lengths revealed that cycles with even numbers of conducted sinus beats were characterized by a significant reduction in the preceding postextrasystolic pause (1441+/-76 msec vs. 1487 +/-59 msec; p less than .001) and second sinus cycle (720 +/- 44 msec vs. 750 +/- 38 msec; p less than .001). Premature ventricular beats were interpolated in 41 additional sequences. Interpolated extrasystoles were separated by the expected even numbers of conducted sinus beats in 39 cases and odd numbers (exceptions) in only two cases. The frequency of exceptions to the usual rules for concealed bigeminy was therefore 2/39 during interpolation and 48/117 without interpolation (p less than .01). This case demonstrates that: 1) a reduction in cycle length may be associated with exceptions to the usual rules for concealed bigeminy, and 2) the frequency of exceptions to concealed bigeminy may be altered by the presence of interpolation. Only one previous case has contained statistical documentation of these circumstances. The diagnosis of a concealed ventricular rhythm may be facilitated by careful analysis at multiple cycle lengths.     

Coronary artery spasm as the cause of myocardial infarction during coronary arteriogarphy.

Catheter-induced coronary artery spasm has been observed frequently. It is usually transient, reacts to the administration of nitroglycerin, and its distribution is generally confined to an area in proximity ot the intubated catheter. A 43-year-old woman with recurrent chest pain was found to have a rather long segment of tight proximal obstruction of the right coronary artery and experienced a myocardial infarction during coronary catheterization. Because of recurrent attacks of severe chest pain, coronary artery bypass surgery was performed which failed to result in significant improvement of her symptoms. Two repeat coronary cineangiograms seven weeks and three years after surgery revealed the proximal right coronary artery to be free of stenotic lesions or of luminal irregularities. After considering possible mechanisms of myocardial necrosis in the presence of normal coronary arteries it is concluded that myocardial necrosis can result from catheter-induced coronary artery spasm in spite of administration of nitroglycerin.     

Perioperative myocardial infarction related to coronary bypass surgery.

Frank lead electrocardiograms were recorded from 149 normal and abnormal adult males using four different electrode placements. All chest electrodes were placed at: (1) the fourth intercostal space level, (2) the fifth intercostal space level, (3) the fourth intercostal space level with V₄ substituted for C, and (4) the fifth intercostal space level with V₄ substituted for C.Differences in mean values of many commonly used amplitudes and orientations were not statistically significant among the four recording methods, but amplitude differences for individual subjects were often large and difficult to predict. When V₄ is substituted for C, as commonly done in some laboratories, R_x decreased and R_z increased by more than 10 per cent in about 40 per cent of the cases. In about 70 per cent of the cases, R_x and R_z changed significantly when electrode level was shifted from the fifth to the fourth intercostal space. For these 70 per cent, it does not appear possible to accurately predict increase or decrease of R_x, R_z, or QRS_m.Analysis programs which depend on individual amplitude measurements are likely to be significantly affected by electrode placement. It is suggested that criteria for analysis programs developed using a specified version of the Frank system should ideally be applied only to electrocardiograms recorded in the same manner.     

Concealed atrial bigeminy and trigeminy.

Patterns indicative of concealed atrial extrasystoles were observed in two patients with frequent premature atrial depolarizations. In the first patient, the predominant pattern was such that most of the numbers (S) of sinus P waves between atrial extrasystoles satisfied the equation S = 3n-1, where n is any positive integer. This pattern is characteristic of concealed trigeminy. Over a sequence of 49 interectopic intervals, this patient vacillated between concealed atrial trigeminy and bigeminy. A second patient displayed a pattern characteristic of the "even number" variant of concealed bigeminy. The numbers of sinus P waves in consecutive interectopic intervals were predominantly even. These various patterns of concealed atrial extrasystoles closely resemble previously reported patterns of concealed ventricular extrasystoles.