Clinical Outcomes of Coronary Artery Bypass Grafting (CABG) in Patients with Mild and Moderate Left Ventricular Dysfunction: A Single Centre Prospective Cohort Study

Technical Summary: Clinical Outcomes of CABG in Mild and Moderate LV Dysfunction

Problem Statement
Coronary artery bypass grafting (CABG) is a well-established revascularization strategy for multivessel coronary artery disease, particularly in patients with severe left ventricular (LV) systolic dysfunction, where survival benefits over medical therapy are documented in landmark trials. However, patients with mild to moderate LV dysfunction represent a clinically heterogeneous group that is frequently under-represented in major randomized studies, despite constituting a substantial portion of contemporary surgical practice. While emerging evidence suggests that even modest reductions in LV ejection fraction (LVEF) correlate with increased perioperative risks and worse mid-term outcomes, there is a need for updated, real-world data to define expected clinical results. This study addresses the gap in knowledge regarding whether the degree of preoperative LV dysfunction (specifically mild vs. moderate) influences postoperative recovery of LVEF and early clinical outcomes.

Methodology
This was a prospective, single-centre observational cohort study conducted at the Government Stanley Medical College and Hospital in Chennai, India.

• Population: The study enrolled 130 adults (aged 18–65) with angiographically proven coronary artery disease undergoing elective CABG. Inclusion criteria required preoperative LVEF between 30% and 54% (measured within two weeks of surgery).
• Exclusion Criteria: Patients requiring emergency CABG, concomitant valve surgery, those with severe LV dysfunction (LVEF <30%), previous cardiac surgery, or significant systemic illness were excluded.
• Stratification: The final analyzable cohort of 118 patients was stratified into two groups based on preoperative LVEF:
  • Mild LV Dysfunction: LVEF 41–53% (n=69).
  • Moderate LV Dysfunction: LVEF 31–40% (n=49).
• Data Collection: Baseline demographic, clinical, angiographic, and echocardiographic data were collected. Perioperative variables included surgical technique, cardiopulmonary bypass times, and graft numbers.
• Follow-up: Assessments were conducted at 30 days and 3–6 months, with echocardiographic reassessment at 6 months. The primary outcome was the change in LVEF; secondary outcomes included in-hospital morbidity, mortality, hospital stay duration, and worsening of LV wall motion.
• Analysis: Statistical analysis utilized parametric and non-parametric tests, multivariable logistic regression, and Kaplan–Meier survival analysis, with significance set at p < 0.05.

Key Results

• Demographics: The moderate dysfunction group was slightly older (mean 55.57 vs. 51.41 years, p=0.013) and had a higher proportion of males (81.63% vs. 65.22%). Baseline comorbidities, smoking history, and prevalence of prior myocardial infarction were comparable. Triple-vessel disease was the predominant angiographic pattern in both cohorts.
• LVEF Improvement: Both groups demonstrated significant improvement in LVEF at follow-up.
  • Baseline: Mild group (46.91 ± 3.0%) vs. Moderate group (37.88 ± 2.78%), p < 0.001.
  • Follow-up (6 months): Mild group (51.06 ± 5.85%) vs. Moderate group (42.39 ± 5.28%), p < 0.001.
  • Magnitude of Change: The absolute improvement in LVEF was comparable between groups: 4.14 ± 4.44% (Mild) vs. 4.51 ± 5.35% (Moderate), with no statistically significant difference (p = 0.69).
• Clinical Outcomes:
  • Mortality: No in-hospital mortality was observed in either group.
  • Hospital Stay: Duration was comparable (34.41 ± 14.27 days for Mild vs. 35.35 ± 17.26 days for Moderate; p = 0.76).
  • Valvular Abnormalities: Post-operative valvular abnormalities were significantly more frequent in the mild LV dysfunction group (47.83%) compared to the moderate group (20.40%; p = 0.004).
  • Wall Motion: Worsening of LV wall motion during the in-hospital period was common in both groups but did not differ significantly (66.67% vs. 59.18%; p = 0.52).

Significance and Claims
The paper claims that CABG is a safe and effective revascularization strategy for patients with both mild and moderate LV systolic dysfunction. The primary significance of the findings lies in demonstrating that:

1. Comparable Recovery: Despite lower absolute LVEF values in the moderate group, the magnitude of functional recovery (improvement in EF) is similar to that of patients with mild dysfunction.
2. Safety Profile: The absence of in-hospital mortality and similar morbidity profiles (hospital stay, wall motion worsening) suggest that moderate LV impairment alone should not preclude surgical intervention, provided appropriate perioperative care is administered.
3. Risk Stratification: The findings suggest that functional recovery and short-term outcomes in this population may be more favorable than predicted by traditional risk models that heavily penalize reduced EF, highlighting the need for individualized clinical assessment.

Limitations
The authors acknowledge the study's limitations, including its single-centre design, modest sample size, and the lack of routine myocardial viability testing, which limits the ability to predict EF recovery based on tissue viability. Additionally, long-term outcomes beyond the mid-term follow-up were not evaluated.