Electrocardiographic diagnosis of myocardial infarction and ischemia during right ventricular pacing

Electrocardiographic diagnosis of acute myocardial infarction in a pacemaker patient: a case report

Background

The electrocardiographic diagnosis of acute myocardial infarction (AMI) in the setting of cardiac pacing is often challenging. The original Sgarbossa criteria proposed in 1996 were demonstrated to be valid for diagnosis of AMI in both ventricular paced rhythm and left bundle branch block. To improve accuracy, the modified Sgarbossa criteria (MSC) were proposed.

Case presentation

We presented a case of electrocardiographic diagnosis of AMI in a pacemaker patient. The Electrocardiogram (ECG) was false negative by using the original Sgarbossa criteria, whereas true positive by the MSC at a ratio of − 0.20.

Conclusions

The application of MSC using an appropriate ratio (− 0.20 or − 0.25) may facilitate a timely diagnosis of AMI. Physicians should carefully choose the appropriate cutoff in a case-by-case basis.

[Cardiac memory following pacemaker implantation]

BACKGROUND

Although T wave inversions due to cardiac memory were described already 50 years ago, little is known about the prevalence and about clinical predictors of this phenomenon.

METHODS

After exclusion of 238 patients due to bundle branch block or pacemaker dependency, a total of 325 consecutive patients were enrolled in this study during routine outpatient control of their pacemaker. A 12-lead standard ECG was obtained in all patients during transient inhibition of pacing therapy.

RESULTS

Cardiac memory could be documented in 115 of 325 patients (35%) and showed a strong association with the amount of ventricular stimulation. The prevalence of cardiac memory was 9% in patients with ≤25% ventricular stimulation and 86% in patients with ≥75% ventricular stimulation.

DISCUSSION

Cardiac memory was observed in one third of patients following pacemaker implantation. The prevalence of cardiac memory in the ECG with intrinsic rhythm is above 80% in patients with frequent ventricular stimulation. Cardiac memory due to ventricular stimulation is benign and should not be confused with similar T wave inversions due to acute coronary syndrome, severe left ventricular hypertrophy, or myocarditis.

Diagnosis of myocardial infarction and ischemia in the setting of bundle branch block and cardiac pacing

The diagnosis of myocardial infarction (MI) in the presence of left bundle branch block (LBBB) or during ventricular pacing (VP) is challenging because of inherent changes in the sequence of ventricular depolarization and repolarization associated with both conditions. Although LBBB and right ventricular (RV) pacing may both produce abnormalities in the ECG, it is often possible to diagnose an acute MI (AMI) or an old MI based on selected morphologic changes. Primary ST-segment changes scoring 3 points or greater according to the Sgarbossa criteria are highly predictive of an AMI in patients with LBBB or RV pacing. The modified Sgarbossa criteria are useful for the diagnosis of AMI in patients with LBBB; however, these criteria have not yet been studied in the setting of RV pacing. Although changes of the QRS complex are not particularly sensitive for the diagnosis of an old MI in the setting of LBBB or RV pacing, the qR complex and Cabrera sign are highly specific for the presence of an old infarct. Diagnosing AMI in the setting of biventricular (BiV) pacing is challenging. To date there is minimal evidence suggesting that the traditional electrocardiographic criteria for diagnosis of AMI in bundle branch block may be applicable to patients with BiV pacing and positive QRS complexes on their ECG in lead V1. This report is a careful review of the electrocardiographic criteria facilitating the diagnosis of acute and remote MI in patients with LBBB and/or VP.

Apical ballooning syndrome (takotsubo cardiomyopathy) after permanent dual-chamber pacemaker implantation

Apical ballooning syndrome, also called takotsubo cardiomyopathy, has been recently reported. It may mimic acute myocardial infarction and is typically observed in postmenopausal women after stressful events. A 75-year-old female after permanent dual chamber pacemaker implant complained of chest pain with repolarization alterations suggesting acute myocardial ischemia. Echocardiography showed a left ventricle with akinesia of the apical portions and reduced global systolic function. The patient was treated with antithrombotic agents and intravenous nitrates. No coronary lesions were found at angiography. At ventriculography, a typical takotsubo-like shape of the left ventricle was observed. The clinical and echocardiographic picture normalized at discharge.