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

Diagnosis of Occlusion Myocardial Infarction in Patients with Left Bundle Branch Block and Paced Rhythms

PURPOSE OF REVIEW

A number of criteria have been developed to aid with the diagnosis of occlusion myocardial infarction (OMI) in patients with left bundle branch block (LBBB) and ventricular paced rhythms (VPR). The current guidelines do not provide clear preference for any specific ECG criteria in LBBB and paced rhythm patients.

RECENT FINDINGS

This review delineates the difficulties of electrocardiographic diagnosis of OMI in both LBBB and VPR patients. We describe the original Sgarbossa and the newer criteria and their diagnostic performances. We highlight the expected changes of newer pacing modalities and how they may interfere with the electrocardiographic diagnosis of OMI. We recommend utilizing the Cai et al. algorithm, which combines clinical assessment with the Smith Modified Sgarbossa ECG criteria, for both LBBB and right ventricular pacing patients with suspected OMI. There is limited data concerning ECG changes of OMI in patients with the newer pacing modalities, such as biventricular, His-bundle, or left bundle branch pacing.

[High-risk ECGs in acute chest pain : Signs of acute ischemia beyond STEMI]

BACKGROUND

Obtaining an electrocardiogram (ECG) is the gold standard for initial diagnostics of atraumatic chest pain. To provide optimal patient care, the treating physician has to be proficient in recognizing early signs of myocardial ischemia. Information from the clinical assessment and typical ECG signs have to be recognized promptly in order to diagnose myocardial ischemia early.

METHODS

A selective literature search in international databases (PubMed, Cochrane Library, Google Scholar) was conducted; current, topic-specific websites and literature were also included and evaluated.

RESULTS

Several subtle ECG abnormalities exist besides the typical ST-elevation myocardial infarction (STEMI) and well-known STEMI equivalents and may point to possible myocardial ischemia.

DISCUSSION

To fully evaluate the ECG in patients with atraumatic chest pain, typical signs of ischemia like STEMI as well as subtle ECG signs should be recognized to allow early cardiac intervention.

Arrhythmia in Acute Myocardial Infarction: A Six-Month Retrospective Analysis From the National Institute of Cardiovascular Diseases

Introduction Acute myocardial infarction (AMI) is a devastating medical emergency that requires immediate pharmacological and radiological intervention. With the advent of techniques such as percutaneous coronary intervention (PCI), pacemakers, and percussion pacing, survival rates have improved significantly. However, there are certain factors and complications associated with AMI that still lead to a high mortality rate, such as old age, advanced heart disease, diabetes mellitus (DM), and arrhythmias. Factors such as the type of arrhythmia, the heart rate, and the level at which dissociation occurs between atrial and ventricular rhythm all influence mortality and morbidity rates. Outcomes are further influenced by the sex of the patient, the type of AMI [ST-elevation myocardial infarction (STEMI) or non-ST-elevation myocardial infarction (NSTEMI)], history of smoking, arrival times at the hospital, presence of hyperglycemia, previous history of cardiac surgery, and the need for a temporary pacemaker or a permanent pacemaker. As with most scientific studies, local data from Pakistan is hard to find on this topic as well. With this study, we hope to contribute valuable information and updates to the study of a developing problem from the developing world. Objective We aimed to analyze the frequency and outcomes of different types of arrhythmia in AMI. Methods This study involved a retrospective observational cohort. It was conducted at the National Institute of Cardiovascular Diseases (NICVD), Karachi from January 2019 to July 2019 (six months). All data were retrieved from the online database at the NICVD. Written consent was obtained from all patients. Patient confidentiality was ensured at all times. Results A total of 500 patients were included in the study. The mean age of our cohort was 56.17 ±14.01 years. NSTEMI was more prevalent than STEMI. Sinus arrhythmia (SA) was the most frequently recorded arrhythmia and had the best survival rates. Atrioventricular (AV) nodal blocks and ventricular tachycardia (VT) had the worst outcomes. The overall mortality rate was 11.4%, and the mean in-hospital length of stay was 2.07 ±1.54 days. Smoking increased mortality in all cases. Conclusions AMI is complicated by several types of arrhythmia. SA is the most common arrhythmia in AMI. Mortality in AMI is largely due to AV nodal blocks and VT. Smoking increases mortality in all cases.

[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.

The role of baseline and post-procedural frontal plane QRS-T angles for cardiac risk assessment in patients with acute STEMI

BACKGROUND

To our knowledge, no study so far investigated the importance of post-procedural frontal QRS-T angle f(QRS-T) in ST segment elevation myocardial infarction (STEMI). The aim of our study was to investigate the role of baseline and post-procedural f(QRS-T) angles for determining high risk STEMI patients, and the success of reperfusion.

METHODS

A total of 248 patients with first acute STEMI that underwent primary percutaneous coronary intervention (pPCI) or thrombolytic therapy (TT) between 2013 and 2014 were included in this study. Baseline f(QRS-T) angle was defined as the angle which measured from the first ECG at the time of hospital admission. Post-procedural (QRS-T) angle was defined according to the treatment strategy as follows: the angle which measured from the post-PCI ECG in patients treated with pPCI; the angle which measured from the ECG taken 90 min after onset of therapy in patients treated with TT.

RESULTS

The baseline (101.9° ± 48.0 vs. 72.1° ± 49.1, p = 0.014) and post-procedural f(QRS-T) angles (95.7° ± 48.1 vs. 58.1° ± 47.1, p = 0.002) were significantly higher in patients who developed in-hospital mortality than the patients who did not develop in-hospital mortality. Also, f(QRS-T) angle measured at 90 min was significantly lower in patients with successful thrombolysis group compared to failed thrombolysis group (53.2° ± 42.8 vs. 77.3° ± 52.9, p = 0.033), whereas baseline f(QRS-T) angle was similar between two groups (78.6° ± 53.4 vs. 78.9° ± 54.0, p = 0.976). Multivariate analysis showed that post-procedural f(QRS-T) angle ≥89.6° (odds ratio: 3.541, 95% confidence interval: 1.235-10.154, p = 0.019), but not baseline f(QRS-T) angle, was independent predictor of in-hospital mortality.

CONCLUSION

f(QRS-T) angle may be used as a beneficial tool for determining high risk patients in acute STEMI. Unlike previous studies, we showed for the first time that that post-procedural f(QRS-T) can predict in-hospital mortality and TT failure.

[Intermittent left bundle branch block - reversal to normal conduction during general anesthesia]

BACKGROUND AND OBJECTIVES

Transient changes in intraoperative cardiac conduction are uncommon. Rare cases of the development or remission of complete left bundle branch block under general and locoregional anesthesia associated with myocardial ischemia, hypertension, tachycardia, and drugs have been reported. Complete left bundle branch block is an important clinical manifestation in some chronic hypertensive patients, which may also be a sign of coronary artery disease, aortic valve disease, or underlying cardiomyopathy. Although usually permanent, it can occur intermittently depending on heart rate (when heart rate exceeds a certain critical value).

CASE REPORT

This is a case of complete left bundle branch block recorded in the preoperative period of urgent surgery that reverted to normal intraoperative conduction under general anesthesia after a decrease in heart rate. It resurfaced, intermittently and in a heart-rate-dependent manner, in the early postoperative period, eventually reverting to normal conduction in a sustained manner during semi-intensive unit monitoring. The test to identify markers of cardiac muscle necrosis was negative. Pain due to the emergency surgical condition and in the early postoperative period may have been the cause of the increase in heart rate up to the critical value, causing blockage.

CONCLUSIONS

Although the development or remission of this blockade under anesthesia is uncommon, the anesthesiologist should be alert to the possibility of its occurrence. It may be benign; however, the correct diagnosis is very important. The electrocardiographic manifestations may mask or be confused with myocardial ischemia, factors that are especially important in a patient under general anesthesia unable to report the characteristic symptoms of ischemia.