INTRODUCTION and BACKGROUND:

Cardiovascular disease (CVD) is the most frequent cause of death globally. Of these deaths, a majority are due to coronary heart disease. The incidence of coronary artery disease (CAD) and cancer have increased owing to changing Lifestyle and environmental modifications. This has occurred in the developed world and is occurring in the developing countries. Patients with CAD are at increased risk of major cardiac events in the perioperative period.

Anaesthesia and perioperative period is associated with high demand on cardiovascular system. Major non cardiac surgery is associated with perioperative cardiac mortality of 0.5-1.5% and major cardiac morbidity of 2-3.5%. This risk increases significantly with underlying CAD. Intraperitoneal, intrathoracic , head and neck surgeries, major urological procedures, neurosurgeries and major orthopaedic surgeries are labelled as intermediate risk surgeries as they are associated with 1-5% incidence of cardiac death and non-fatal myocardial infarction within 30 days of surgery. Patients undergoing major cancer surgeries are generally elderly with risk factors for coronary artery disease and low dose standard lung C.T. scans that are done as a standard of care as part of the pre-operative evaluation can give information about the coronary artery calcium (CAC) deposition. As part of anaesthesia workup most of these patients undergo further cardiac evaluation in form of stress test (either treadmill test or dobutamine stress ECHO)

Multiple predictors of the severity of CVD are available, the most effective of them being Coronary Artery Calcification (CAC). Detection of coronary artery calcification (CAC) is a strong predictor of CAD, cardiovascular events, and all-cause mortality. CAC is usually quantified on dedicated 3 mm sliced computed tomography (CT) scans that are electrocardiography (ECG) gated, so as to minimize motion artifact from the beating heart and provide relatively fine cuts from the beating heart. Patients posted for Cancer surgeries undergo standard 6 mm chest CTs for metastatic workup, but CAC is not usually quantified. Calcium within the coronary arteries can be easily recognized on these scans, and prior studies have evaluated CAC on lung CTs for CAD screening in smokers at high risk for lung cancer.

CAC is a marker of the presence and severity of coronary atherosclerosis. Its presence in asymptomatic subjects indicates the existence of subclinical coronary artery disease (CAD). The American College of Cardiology Foundation (ACCF) and American College of Cardiology (AHA) in 2010 gave class IIa recommendation for measurement of CAC for cardiovascular risk assessment in asymptomatic adults at intermediate risk. In 2012 European Society of Cardiology awarded a similar class IIa recommendation, and suggested CAC for CV risk assessment in asymptomatic adults at moderate risk.

Generally CAC is reported using Agatston score which is a semi-automated tool to calculate a score based on the extent of coronary artery calcification detected by an unenhanced low-dose CT scan in patients undergoing cardiac CT. It allows for an early risk stratification as patients with a high Agatston score (>160) have an increased risk for a major adverse cardiac event (MACE). Ordinal scoring by Shemesh et al has shown very good correlation with Agatston scoring for prediction of outcome of cardiovascular disease.

Our study aims to recognize the incidence and severity of CAC on standard CT chest by using the visual scale and then correlate these scores with the patients’ clinical condition preoperatively as well as the intraoperative and postoperative cardiac events. The visual categorization of this CAC in four categories can be generated for risk assessment of CHD and is strongly associated with the outcome.

Coronary artery calcification (CAC) will be assessed and categorized as:

i)                    Visual Score = 0 – No CAC detected

     ii)    Visual Score = 1 to 4 – Mild CAC

    iii)   Visual Score = 5 to7 – Moderate CAC

    iv)   Visual Score = 8 to 12 Severe CAC

The visual scoring correlates well with the dedicated CAC scoring like Agatston scoring and might predict clinically significant CAC. Each of the four main coronary arteries will be identified (left main, left anterior descending, circumflex, and right). Calcification in each artery will be categorized as absent, mild, moderate, or severe and scored by the radiologist as 0, 1, 2, or 3, respectively. Calcification is classified as mild when less than one-third of the length of the entire artery shows calcification, moderate when one-third to two-thirds of the artery shows calcification, and severe when more than two-thirds of the artery shows calcification. With four arteries thus scored, each subject receives a CAC score ranging from 0 to 12.

When predicting the perioperative complications, the CAC will be correlated with certain other factors to provide a more wholistic report. These include the revised cardiac Risk index, and the NYHA scoring system preoperatively.

Lees Revised Cardiac Risk Index- Each risk factor is assigned one point.

1. High-risk surgical procedures

- Intraperitoneal

- Intrathoracic

- Supra-inguinal vascular

2. History of ischemic heart disease

- History of myocardial infarction

- History of positive exercise test

- Current complain of chest pain considered secondary to myocardial ischemia

- Use of nitrate therapy

- ECG with pathological Q waves

3. History of congestive heart failure

- History of congestive heart failure

- Pulmonary edema

- Paroxysmal nocturnal dyspnea

- Bilateral rales or S3 gallop

- Chest radiograph showing pulmonary vascular redistribution

4. History of cerebrovascular disease

- History of transient ischemic attack or stroke

5. Preoperative treatment with insulin

6. Preoperative serum creatinine > 2.0 mg/dL

RISK OF MAJOR CARDIAC EVENT

Points Class Risk

0  I 0.4%

1  II 0.9%

2  III 6.6%

3  or more IV 11%

NYHA classification

I-No limitation of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, dyspnea (shortness of breath).

II- Slight limitation of physical activity. Comfortable at rest. Ordinary physical activity results in fatigue, palpitation, dyspnea (shortness of breath).

III- Marked limitation of physical activity. Comfortable at rest. Less than ordinary activity causes fatigue, palpitation, or dyspnea.

IV- Unable to carry on any physical activity without discomfort. Symptoms of heart failure at rest. If any physical activity is undertaken, discomfort increases.

Intraoperative and Postoperative cardiac events will be recorded as

1. Has the patient undergone diagnostic test or therapy during present admission for any of the following?

a. new MI

b. Ischameia or hypotension requiring drug therapy or fluid therapy (fluid bolus >1lt over 2 hours or fluid infusion >200ml/hr)

c. Atrial or Ventricular arrhythmias

d. new ECHO findings

e. cardiogenic pulmonary edema or addition of new anticoagulation

The patients will be followed up until discharge from the hospital.

AIMS and OBJECTIVES:

PRIMARY OBJECTIVE: To Assess the frequency and severity of CAC on standard CT chest in patients undergoing major thoracic, hepatic and pancreatic surgeries and its grading based on Visual score.

SECONDARY OBJECTIVE: To correlate the severity of the CAC on patients clinical condition, investigations preoperatively, intraoperatively and postoperatively.

MATERIALS and METHODS:

Type of study: Prospective observational study as a part of dissertation at TMH, Mumbai

Inclusion criteria: All patients above 18 years of age undergoing major thoracic, pancreatic and hepatic surgeries where standard CT thorax is part of a regular pre operative investigation.

Exclusion criteria: Paediatric patients (under the age of 18 years).

               Patients deemed inoperable.

METHODOLOGY:

After obtaining approval from hospital ethics committee, short informed consent will be obtained from patients fulfilling the criteria. Patients undergoing CT thorax as a routine pre operative investigation will be evaluated for coronary artery calcification and graded according to the visual scale by the radiologist . The demographic profile of consenting patient will be recorded i.e. age, sex, ASA physical status, weight, BMI, surgery, NYHA class will be noted. Preoperative investigations and optimization will be according to the PAC anesthetist. Patients’ induction & maintenance of general anaesthesia will be as per the decision of OT anaesthetist. Postoperatively, the patient will be followed up until discharge from the hospital. We will then proceed to corelate the CAC based on the Perioperative criteria and clinical condition of the patient as stated above.

STATISTICAL ANALYSIS AND RESULTS:

There will be no conflict of interest