European Journal of Cardiovascular Medicine

Acute coronary syndrome (ACS) ranks among the causes of morbidity and mortality globally, and it frequently presents with serious complications affecting short- and long-term prognosis. Aritrioventricular (AV) block is one such severe complication that represents a conduction abnormality impairing the customary electrical transmission between the atria and ventricles, provoking hemodynamic instability and enhancing mortality [1]. The presence of AV block in the context of ACS, especially in inferior wall MI, has been documented extensively, with rates of occurrence between 3% and 8% across different studies [2]. Despite this, its effects on clinical outcomes and the best revascularization strategy are topics of continued research.

Revascularization is essential to restore the perfusion of the myocardial tissue and enhance overall cardiac function among ACS patients. The two major revascularization methods are percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG) [3]. The intervention is determined by several factors such as the site of infarct, severity of coronary artery disease (CAD), and comorbidities. In ACS with AV block, early restoration of coronary perfusion can help in recovery of the conduction system and decrease the risk of persistent bradyarrhythmias necessitating permanent pacemaker implantation [4].

The pathophysiology of AV block in ACS is multifactorial, with ischemia-induced injury to the conduction system being one of the major mechanisms. Temporary AV block in inadequate MI is typically attributed to ischemia affecting the atrioventricular node, which is typically supplied by the right coronary artery (RCA) [5]. However, anterior MI, involving the left anterior descending (LAD) artery, might cause greater damage, involving the His-Purkinje system and resulting in a greater possibility of persistent AV block and pacemaker implantation [6]. In light of these differences, a personalized strategy for revascularization is needed to maximize results and reduce conduction-related issues.

Although benefits of PCI and CABG to enhance survival and myocardial recovery in ACS patients have been established, sparse evidence is available about their individual effects on resolution of AV block and long-term conduction outcomes. Some research indicates that early PCI is linked with greater chances of AV conduction recovery, especially in patients with transient AV block due to inferior MI [7]. On the other hand, CABG can be opted for in patients with multivessel disease or involvement of the left main coronary artery, in which surgical revascularization is seen to yield better long-term outcomes [8, 9].

With the clinical importance of AV block in ACS and the possible influence of various revascularization strategies, additional studies are necessary to provide evidence-based guidelines for the best management. Our objective is to contrast the prognosis of PCI, CABG, and conservative treatment in ACS patients with AV block on survival, myocardial improvement, and restoration of the conduction system. With the definition of the ideal method for high-risk patients, we hope to increase clinical choice and better global prognosis [10].

Study Design and Setting

This prospective observational study was conducted at a tertiary cardiac hospital in Ahmedabad, Gujarat, between December 1, 2018, and March 30, 2020. The study included patients diagnosed with acute coronary syndrome (ACS) presenting with atrioventricular (AV) conduction defects.

Study Population

Patients with ACS, including ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI), who developed AV block at presentation or during treatment before revascularization were enrolled. STEMI was defined as new ST elevation at the J point in two contiguous leads (≥0.1 mV in all leads except V2-V3, with specific cut-offs for gender and age) or new left bundle branch block (LBBB) with elevated cardiac biomarkers [10]. NSTEMI was diagnosed in cases with elevated troponin levels and ECG changes without ST-segment elevation.

Ethical Approval and Data Collection

The study was approved by the Institutional Ethics Committee, and written informed consent was obtained from all participants. Out of 150 eligible patients, 34 were excluded based on medical history or lack of CAG, leaving a final study population of 116 patients. Data were collected using a standardized proforma, including demographic details, comorbidities, systemic examination findings, laboratory parameters, and electrocardiographic and echocardiographic assessments [12]. Hypertension, diabetes, and congestive heart failure were defined based on ongoing pharmacological treatment.

Interventions and Follow-Up

Percutaneous coronary intervention (PCI) was performed following standard interventional guidelines. Temporary pacemaker implantation was considered in patients with symptomatic high-degree AV block. Post-procedure, patients were monitored for AV block resolution. Holter monitoring was conducted before discharge in patients with persistent AV block. Patients without conduction abnormalities were discharged 72 hours post-revascularization [13]. Follow-up evaluations were conducted at 1 month, 6 months, and 1 year to assess AV block resolution.

Statistical Analysis

Data were recorded in Microsoft Excel 2010 and analyzed using Epi Info version 7.1. Continuous variables were presented as mean ± standard deviation, while categorical variables were expressed as frequencies and percentages [14]. Comparative analyses were performed based on clinical features, vessel involvement, culprit artery, presence of high-degree AV block, need for temporary or permanent pacing, and AV block recovery over follow-up.

A total of 150 patients were initially enrolled in the study, of which 34 were excluded due to prior medical history or unavailability of coronary angiography. Data from 116 patients were analyzed. The mean age of patients was 61.1 ± 10.2 years, with the majority (55.2%) belonging to the 61–80 years age group (Figure 1). Males constituted 75.9% of the study population, with a Male: Female ratio of 3.14:1 (Figure 2).

Figure 1. Distribution of patients according to age group.

Figure 2. Gender-wise distribution of patients.

Comorbidities were present in 92.2% of patients. The most common was diabetes mellitus and hypertension (47.4%), followed by isolated hypertension (23.3%) and diabetes mellitus (17.2%) (Figure 3).

Figure 3. Distribution of patients according to comorbidities.

Inferior wall myocardial infarction (IWMI) was the most prevalent diagnosis (78.5%), with 65.5% having isolated IWMI. Anterior wall MI (12.2%) and NSTEMI (9.5%) were less common (Figure 4).

Figure 4. Distribution of patients according to diagnosis of myocardial infarction.

Among the different types of atrioventricular (AV) blocks, complete heart block (CHB) was the most common (65.5%), followed by second-degree AV block (19.8%) and first-degree AV block (14.7%) (Figure 5). A significant number of patients had progression of AV block before hospitalization, with 12 out of 35 patients with initial first-degree AV block developing CHB, and 6 patients with second-degree AV block progressing to CHB.

Figure 5. Distribution of patients according to type of atrioventricular (AV) block.

Following percutaneous coronary intervention (PCI), patients were monitored for AV block resolution at discharge, 1 month, 6 months, and 1 year. The need for temporary and permanent pacemaker implantation was also analyzed.

Post-Revascularization Recovery of AV Block

A total of 116 patients were enrolled in the study. Among them, 24 patients required temporary pacemaker implantation (TPI) on admission, while the remaining 92 patients did not require TPI. Revascularization was performed using percutaneous transluminal coronary angioplasty (PTCA) and CABG. Post-revascularization recovery was assessed during the hospital stay and up to one-year post-discharge.

Recovery in Patients on TPI (n=24)

Within the first hour, 11 patients recovered, remained on TPI backup with Holter monitoring, showed no AV block, and had their TPI removed before being discharged after 72 hours. Within 24 hours, six patients recovered, underwent Holter monitoring, and were discharged after 72 hours. However, two patients with high-grade AV block, lower LVEF, and triple vessel disease succumbed to pump failure within 24 hours. At 72 hours, five patients showed no recovery, continued on TPI for a week, and were considered for permanent pacemaker implantation (PPI) due to persistent AV block. These non-recovered patients were older, had multi-vessel disease, delayed presentation, and low LVEF. Among them, three had LAD as the culprit vessel, while two had RCA involvement with proximal LAD disease. Among the 92 patients not requiring TPI, 79 recovered and were discharged after 72 hours, while three with first-degree AV block recovered within 24 hours and were discharged. Three patients with persistent high-grade AV block, low LVEF, and ostial lesions did not survive within the first 24 hours. Two patients recovered at one week and were discharged, while three patients had intermittent high-grade AV block but stable escape rhythm without symptoms and were considered for PPI after seven days. Ultimately, eight patients underwent PPI, five patients died, and the remaining 111 were discharged and followed up for AV block recovery.

Table 1. Recovery Outcomes in Patients with and without Temporary Pacing Intervention (TPI)

At the one-month follow-up, among 25 patients with LAVB, 21 (84%) showed complete recovery, while four (16%) had persistent conduction abnormalities. In contrast, among 86 patients with HAVB, 52 (60.5%) recovered, whereas 34 (39.5%) exhibited persistent AV block. At six months, an additional two LAVB patients (total recovery 92%) and 12 HAVB patients (total recovery 74.4%) showed improvement, but two LAVB and 22 HAVB patients continued to have conduction defects. By the one-year follow-up, 24 (96%) LAVB patients achieved full recovery, while one patient had residual conduction abnormalities. In HAVB patients, 66 (76.7%) demonstrated complete resolution, whereas 20 (23.3%) required permanent pacemaker implantation (Table 1). The recovery trend indicated a higher likelihood of spontaneous resolution in LAVB cases compared to HAVB, with a significant proportion of HAVB patients requiring long-term pacing support.

Table 2. Clinical and Angiographic Characteristics of Patients with Low-Grade and High-Grade AV Blocks

The results indicate that among LAVB patients, first-degree AV block was the most common presentation (n=17), followed by Mobitz type I (n=8) and Mobitz type II (n=4). In HAVB patients, CHB was predominant (n=76), with 2:1 AV block observed in 11 cases. The mean age of HAVB patients (63.7 ± 8.4 years) was significantly higher than LAVB patients (52 ± 13.5 years, p<0.001). Male predominance was observed across groups, but the difference was not statistically significant (p=0.28).

Comorbidities showed significant variation, with DM+HTN being more prevalent in CHB patients (55.3%, p=0.0004). Hypertension alone was highly associated with Mobitz type II (100%, p<0.0001). The majority of patients had IWMI, with no significant difference across subgroups (p=0.65). LVEF was significantly lower in CHB patients (37.9 ± 5.9%, p=0.03), and those with Mobitz type II (40 ± 0.1%) and 2:1 AV block (40 ± 6.7%) also had reduced LVEF.

Angiography revealed that single-vessel disease (SVD) was more common in Mobitz type II (100%, p=0.001), while three-vessel disease (TVD) was significantly associated with CHB (56.6%, p=0.02). RCA was the most frequently affected vessel across all groups (p=0.12). Percutaneous transluminal coronary angioplasty (PTCA) was the primary revascularization method across all patients, with a few undergoing PTCA followed by CABG. TPI was significantly more frequent in Mobitz type II (50%, p=0.04) and 2:1 AV block (27.3%).

Permanent pacemaker insertion was required in 9.2% of CHB patients, 12.5% of Mobitz type I cases, and 9.1% of 2:1 AV block cases, but none in first-degree or Mobitz type II cases. Overall, LAVB patients had better outcomes with lower intervention rates, while HAVB, especially CHB, had more severe disease characteristics and required long-term pacing support [15].

This research points out the clinical result of AV block recovery after percutaneous coronary intervention (PCI) in myocardial infarction patients. Of 116 patients examined, inferior wall myocardial infarction (IWMI) was the leading diagnosis, and complete heart block (CHB) was the most frequent type of AV block. Temporary pacemaker implantation (TPI) was necessary in 24 patients, with 46% of them exhibiting recovery within the initial 24 hours and 21% undergoing permanent pacemaker implantation (PPI) for persistent conduction defects. The trend of recovery after one year showed that spontaneous recovery was more likely in low-grade AV block (LAVB) patients, with 96% being completely recovered as opposed to 76.7% in high-grade AV block (HAVB) patients. The requirement for permanent pacing was most strongly related to advanced age, multi-vessel disease, low LVEF, and late presentation. The findings underscore the prognostic importance of initial AV block categorization and confirm the necessity for strict follow-up and early treatment in high-risk individuals.

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