Anterior left ventricular aneurysm: factors associated with the development of sustained ventricular tachycardia

Digital 3D image reconstruction of ventriculocapillary communication as revealed in one case after transmyocardial laser revascularization

TMR (Transmyocardial Laserrevascularization) was performed on the partially dyskinetic left ventricular anterior wall with stenotic coronary blood supply in a 61 year old woman with a history of angina and myocardial infarction. As an ischemic aneurysm developed in the anteroapical region of the TMR treated area, it became clear that TMR did not provide a substitute for coronary blood supply in this very heart region. The aneurysm was removed surgically 7 months after TMR and showed histopathologic features of an acute aneurysm. Three-dimensional image analysis helped prove the presence of linear tracks through several serial sections which were not easily visible in routine histology sections. Also, three-dimensional vessel reconstruction showed a connection between a small endocardial pit on one serial section with the capillary network in the adjacent serial sections. The results should not be generalized, as currently aneurysmectomy is an end point not reached by the majority of TMR-treated patients.

Postinfarction ventricular aneurysms

Ventricular aneurysms are circumscribed, thin-walled fibrous, noncontractile outpouchings of the ventricle. The majority are apically located, true aneurysms of the left ventricle (LV) that occur as a consequence of transmural myocardial infarction (MI). The precursor of aneurysm formation appears to be infarct expansion early after acute MI and occurrence generally relates to infarct size. The presence of underlying hypertension and the use of steroids and nonsteroidal antiinflammatory agents may promote aneurysm formation. The clinical sequelae include congestive heart failure (CHF), thromboembolism, angina pectoris, and ventricular tachyarrhythmias. Late rupture is a particular complication of false aneurysms in which the pericardium is the aneurysm wall. The diagnosis may be suspected by the clinical finding of a diffuse, pansystolic apical thrust, persistent ST-segment elevation on the electrocardiogram, and distortion of the cardiac silhouette on chest x-ray. This can be confirmed using echocardiography, radionuclide ventriculography, and cardiac catheterization. The latter has the additional advantage of being able to delineate the coronary anatomy. Management involves prevention, specific therapy for the various clinical manifestations, and surgery. Therapeutic interventions with thrombolytic agents, aspirin, heparin, and beta blockers that are applied early in the evolution of an MI may limit infarction size, thereby reducing the tendency toward infarct expansion and aneurysm formation. Patients with mild CHF can usually be controlled with the standard combination of angiotensin-converting enzyme inhibitors, diuretics, and digoxin. Thromboembolism is best prevented by anticoagulation with warfarin for at least 3 months after the acute MI. The choice of pharmacotherapy for ventricular tachyarrhythmias should be guided by electrophysiologic studies. The treatment of patients with angina pectoris utilizes conventional therapeutic modalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of subendocardial resection on sinus rhythm endocardial electrogram abnormalities

BACKGROUND

Patients with sustained ventricular tachycardia after acute myocardial infarction frequently have characteristic abnormalities of left ventricular endocardial electrical activity, including fractionated (prolonged, multicomponent, low-amplitude), split (having discrete widely separated deflections), and late (extending after the end of the QRS complex) electrograms. The exact cause and source of these electrograms are not clear.

METHODS AND RESULTS

In this study, endocardial electrograms from 18 patients were recorded with a 20-electrode array from the same area immediately before and immediately after resection of subendocardial tissue at the time of surgery for ventricular tachycardia. Electrograms could be compared before and after resection from 298 of 360 (83%) of the electrodes. Before resection, split electrograms were present in 130 (44%) and late components in 81 (27%) of the recordings. Recordings made after resection showed fewer abnormalities, including complete absence of split electrograms as well as all previously recorded late components (P < .02). Mean electrogram amplitude increased from 0.5 +/- 0.8 to 1.0 +/- 1.6 mV (P < .0001) because of removal of the attenuating effect of endocardial scar; mean duration decreased from 112 +/- 38 to 65 +/- 27 ms (P < .0001) mainly because of loss of late and split components. Overall electrogram contour was very similar aside from these changes.

CONCLUSIONS

These data show that (1) some of the signal recorded on the endocardial surface is derived from deeper tissue layers and (2) split and late electrogram components appear to be generated by cells in the superficial endocardial layers, since they are eradicated by removal of this tissue. These findings correspond well with previous histological studies of resection specimens that show bundles of surviving muscle cells separated by layers of dense scar that act as an insulator.

Three distinct patterns of ventricular activation in infarcted human hearts. An intraoperative cardiac mapping study during sinus rhythm

BACKGROUND

Comprehensive data based on single-beat analysis of the ventricular activation sequence during sinus rhythm in infarcted hearts are currently not available. It was the aim of our study (1) to measure and analyze these activation sequences on the epicardial surface of the right and left ventricles and on the left ventricular endocardial surface, and (2) to correlate specific activation patterns with the surface ECG.

METHODS AND RESULTS

Isochronal maps were computed from 127 endocardial and epicardial unipolar electrograms recorded simultaneously during sinus rhythm in 45 post-myocardial infarction patients operated on for recurrent ventricular tachycardia (age, 57 +/- 10 years [mean +/- SD], left ventricular ejection fraction, 29 +/- 9%). Patients with bundle-branch block, but not with intraventricular conduction defects, were excluded. Data such as the timing of initial and terminal activation, the number of breakthroughs, the total activation time, and the number of ventricular segments without activation were measured and analyzed according to location of the myocardial infarction. The global epicardial activation was characterized in all patients by a widespread initial breakthrough on the anterior right ventricle (16 +/- 8 milliseconds after QRS onset), which was followed by one or two other breakthroughs in 65% of patients. Subsequently, three characteristic epicardial patterns of the activation spread were found: (1) radial, from the right to the left ventricle, found in all patients with inferoposterior myocardial infarction; (2) counterclockwise rotation, in which posteroseptal crossing preceded the anteroseptal crossing, found in 38% of patients with anterior myocardial infarction; and (3) pincerlike encirclement, in which both septal crossings and/or breakthroughs occurred nearly simultaneously and merged at the left ventricular free wall (typical for apical involvement in anterior and combined myocardial infarction). The simultaneous presence of multiple major activation wave fronts typically found in patients with the pincerlike activation pattern was reflected on the surface ECG by multiphasic, notched QRS complexes. Activation delay was observed in 89% of patients, and terminal activation was topographically related to myocardial infarction in 94% of patients. Delayed activation exceeding the surface QRS was observed in 11% and 31% of cases on the endocardium and epicardium, respectively.

CONCLUSIONS

These results offer a solid basis for a more precise interpretation of a wide range of electrophysiological data and provide a framework for future investigations of surface ECG reflections of endocardial and epicardial activation patterns recorded in patients with chronic myocardial infarction.

Detection and localization of prolonged epicardial electrograms with 64-lead body surface signal-averaged electrocardiography

BACKGROUND

Prolonged, fractionated ventricular electrograms often are detectable after myocardial infarction and are a marker for an arrhythmia-prone state. QRS late potentials detected on the body surface with signal-averaged electrocardiography (SAECG) are thought to arise from the diseased tissue that generates prolonged ventricular electrograms and as such are also a marker for arrhythmias. A limitation of the current SAECG technique is that recordings are obtained from only three bipolar lead pairs. Because late potentials probably arise from multiple small sources in the heart, more extensive sampling of the body surface may contribute additional information to the SAECG: The present study investigates the additional sensitivity of SAECG using 64 body surface leads in detecting prolonged epicardial electrograms and examines its use in determining the epicardial location of prolonged electrograms.

METHODS AND RESULTS

Dogs were studied before and 5-10 days after either lateral left ventricular (n = 13) or right ventricular (n = 8) myocardial infarction. Greater prolongation of signal-averaged QRS duration was detected with 64-lead SAECG (postinfarction QRS duration, 100.3 +/- 16.3 msec) than with three-lead SAECG (postinfarction QRS duration, 89.4 +/- 10.1, p = 0.0005). Nineteen of the 21 dogs (90%) had prolonged epicardial electrograms detected over the infarct. The correlation between epicardial electrogram duration and signal-averaged QRS duration calculated from individual leads was much better for 64-lead SAECG (r = 0.88, p less than 0.0001) than for three-lead SAECG (r = 0.53, p = 0.01), and the difference was most marked in cases with longer electrogram durations (more than 100 msec). Local late potential maxima on the thorax after lateral left ventricular infarction were located to the left and inferior compared with those after right ventricular infarction (p = 0.006).

CONCLUSIONS

SAECG with more extensive recording from the body surface using 64 leads detects greater QRS prolongation than three-lead SAECG, and the longer QRS durations detected correspond to the duration of prolonged epicardial electrograms. Body surface location of late potentials corresponds to the epicardial location of the prolonged electrograms. This application of body surface mapping techniques to SAECG may permit more sensitive detection of arrhythmia-prone states and may aid in identifying arrhythmia sources.

Relation between ventricular late endocardial activity during intraoperative endocardial mapping and low-amplitude signals within the terminal QRS complex on the signal-averaged surface electrocardiogram

Noninvasive recording of ventricular late potentials and intraoperative endocardial mapping at 36 sites were performed in 24 patients with left ventricular aneurysm and drug-resistant sustained ventricular tachycardia due to coronary artery disease. Their mean age was 55 +/- 8 years. Mean ejection fraction was 28 +/- 12%. For detection of late potentials on the signal-averaged QRS complex, 3 different algorithms were used. Late potentials were found in 54, 67 and 67% of the patients, respectively. In patients with a late potential on the signal-averaged electrocardiogram (ECG), delayed local activation (greater than 40 ms beyond the QRS complex on the intraoperative surface ECG) was recorded at 5.5, 5.5 and 5.6 endocardial sites. In patients without a late potential, this type of delayed local activation was detected at 2.4, 1.1 and 0.9 of 36 endocardial sites, respectively (p less than 0.05; p less than 0.01; p less than 0.002). The mean delay of local endocardial activity was 38, 35 and 37 ms in patients with a late potential on the body surface recording versus 20, 19 and 11 ms, respectively, in patients without a late potential (p less than 0.05; p less than 0.05; p less than 0.002). There was no correlation between the duration or amplitude of the late potential, if present, and the number of endocardial sites exhibiting delayed activity (r = -0.23, r = -0.05, r = 0.21; correlation not significant for each) or the mean duration of the endocardial delayed activity (r = -0.25, r = -0.14, r = -0.07; correlation not significant for each). These results indicate that the presence of late potentials on the signal-averaged surface ECG is related to the mean duration of endocardial late activity as well as to the number of endocardial sites exhibiting a given degree of delayed activation. Thus, it is dependent on the mass of slowly activated tissue. However, a direct conclusion from the duration or the amplitude of a late potential to the amount of delayed activation or the extent of endocardial time delay does not seem possible.