Clinical and Angiographic Profile in Non-ST Elevation Acute Coronary Syndrome (NSTE-ACS) and Chronic Stable Angina: A Tertiary Care Centre-Based Cohort Study From Southern Indian Population

Purpose This study aimed to assess the clinico-demographic profile, risk factors, and pattern of coronary involvement in non-ST elevation acute coronary syndrome (NSTE-ACS) and chronic stable angina (CSA). Methods This was a retrospective study conducted in a tertiary care hospital catering mainly to the rural population in Southern India from January 2020 to July 2022. Data from 333 patients with NSTE-ACS and CSA were analyzed during the study period for the clinico-demographic profile, risk factors, and pattern of coronary involvement in angiography. Results The mean age at presentation was 56.05±9.31. Significant obstructive coronary artery disease was present in 234 (70.3%) patients. Overall, single, double, and triple vessel disease occurred in 26%, 20%, and 32.4% of patients with NSTE-ACS and chronic stable angina. Sixty percent of the diabetic and hypertensive patients (n=92/153) had multivessel involvement. Left main coronary artery disease was present in 40 patients (12%). Conclusion Unstable angina was the most common clinical presentation. Left anterior descending (LAD) was the most common coronary vessel to be involved with occurrence of triple vessel disease in 32% of the study population. Multivessel involvement was more common in the diabetic and hypertensive groups.


Introduction
Ischemic heart disease may manifest as either chronic stable angina (CSA) or acute coronary syndrome (ACS). The spectrum of ACS includes ST elevation myocardial infarction (STEMI) and non-ST elevation ACS (NSTE-ACS) which comprises unstable angina and non-ST elevation MI (NSTEMI). The proportion of ACS attributed to NSTEMI continues to increase, while STEMI is declining. This study aimed to assess the coronary angiographic profile in NSTE-ACS and CSA in the Southern Indian population.

Materials And Methods
This was an observational study conducted at Thoothukudi Medical College and Hospital over a period of two years from April 2020 to July 2022. The tertiary care center caters to the rural population of Southern India in Tamil Nadu. The study was done as per the ethical standards set by the Institute Ethics Committee following the 1964 Helsinki Declaration and its amendments. There was a waiver of consent since it was a record-based study and the protocol for the study was approved by the institute ethics committee, Thoothukudi Medical College.
Records of 333 patients with NSTE-ACS and chronic stable angina admitted to Thoothukudi Medical College were analyzed. The patients were categorized as unstable angina, NSTEMI, and CSA. Valvular heart disease and cardiomyopathy were excluded from the study. Demographic details including age and gender were recorded in a predesigned clinical proforma. Any history of smoking, past history of coronary artery disease, 1 and presence of comorbidities, such as diabetes and hypertension, were recorded. The angiographic details of the study population were entered.

Outcome measures
Coronary stenosis was classified as moderate if the narrowing was between 50% and 70% and as severe and significant when the diameter reduction was 70% or more in at least one of the major epicardial coronary arteries. Obstructive coronary artery disease (CAD) was also defined as at least 50% stenosis of the left main coronary artery (LMCA). Normal coronaries referred to the absence of any disease in the left anterior descending (LAD), left circumflex (LCX) and its branches, right coronary artery (RCA), and LMCA. Based on the involvement of the number of vessels, they were further classified as single vessel, double vessel, and triple vessel disease [1].

Statistical analysis
Data were analyzed using the software STATA 15.0 (Texas, USA: Stata Corp.). The normality of the continuous variables was tested and mean with standard deviation was used to present Gaussian variables and median with range is used to present non-Gaussian variables. The groups were compared using Fisher's exact test or chi-square test for categorical variables and Student's t-test for continuous variables.         Left anterior descending (LAD) artery was the most common coronary vessel to be involved (n=184) and LMCA was involved only in 40 patients. On analysis of the multivessel involvement group, 70% were male; 57% were diabetic; 50% were hypertensive and 56% presented with unstable angina (

Main findings with interpretation
The mean age at presentation of NSTE-ACS was 56.11±9.35 years with a much earlier age at presentation in the male population (55.49±9.63). The disease presentation in the Southern Indian population is much earlier when compared to Western literature where the average age ranges from 60 to 70 years [2][3][4]. Similarly, the mean age at presentation of chronic stable angina was 56.7±8.8 years. Whereas the Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) trial showed the mean age at presentation to be 62±10 years [5]. The mean age at presentation as per the current study is 56 years which is similar to other Indian studies [6]. The identification of the background risk factors for such earlier presentation in Indian population will aid in devising apt preventive strategies.
Predominantly, the male gender was affected with the disease in a proportion of 71.1% and 67.5% in the NSTE-ACS and chronic stable angina groups, respectively. Third Randomized Intervention Trial of Unstable Angina (RITA-3) and The Treat Angina with Aggrastat and Determine Cost of Therapy with an Invasive or Conservative Strategy (TACTICS) Thrombolysis in Myocardial Infarction (TIMI)-18 (TACTICS-TIMI-18) trial also had similar male-affected study groups of 63% and 66%, respectively [7,8]. The COURAGE trial and International Study of Comparative Health Effectiveness With Medical and Invasive Approaches (ISCHEMIA) trial, respectively, report a presentation of CSA in 85% and 77.4% males, while our study in comparison reported CSA in 67.5% males [5,9]. The major associated factors include diabetes mellitus, hypertension, and smoking in the index study. The striking difference from the Western cohort is the increased prevalence of comorbidities, such as hypertension and diabetes mellitus, in Indian population. Invasive versus Conservative Treatment in Unstable Coronary Syndromes (ICTUS) trial results showed only 14% patients with diabetes mellitus in comparison to 47% patients in this study [10]. Further multivessel involvement in the diabetic group with earlier age of occurrence emphasizes the critical need for diabetes control and prevention measures to curtail the rising trend of CAD in India [11].
On analysis of the angiographic patterns of CAD in NSTE-ACS, 70% had significant obstructive CAD with LAD being the most common vessel to be involved (54.1%). This observation is consistent with other studies which show LAD (50%) as the most common culprit vessel [12,13]. Normal coronaries occurred in 4.8% with non-obstructive lesions in 13.5% patients. LMCA disease occurred in 9.8% patients of NSTE-ACS group which is similar to the Veterans Affairs Non-Q-Wave Infarction Strategies in Hospital (VANQWISH) trial and FRagmin and Fast Revascularization during Instability in Coronary Artery Disease (FRISC-II) trial wherein the reported involvement was 8% [2,3]. The NSTE-ACS patients had predominant multivessel involvement with 31.2% triple vessel disease and 20.1% double vessel disease. These findings are similar to the data from landmark trials which are summarized in Table 7.

Strengths and limitations
The strength of the study is the in-depth analysis of the angiographic profile and risk characterization of NSTE-ACS. While most of the studies are from Western literature, the study fills the lacunae of a dearth of knowledge about the disease characteristics in the Southern Indian population. The limitations include the sample size and retrospective nature of the study. Future prospective studies and risk factor analysis with follow-up will aid in the risk categorization, prognostication, and targeted preventive measures in the