Associate Director, Cardiology, Max Hospital, Gurugram
Part 3 of 10 in Diagnosis and Management of Ischemic Heart Disease
ECG and Cardiac Biomarkers: The Two Investigations That Diagnose a Heart Attack
September 4, 2026
Once acute coronary syndrome is suspected, Dr. Rohit Goel narrowed the workup to two investigations that matter most: the 12-lead ECG and cardiac biomarkers, backed up by a chest X-ray when the picture is unclear.
The ECG comes first
A 12-lead ECG is, in Dr. Goel's words, the most urgent investigation in a patient with suspected acute coronary syndrome. ST elevation, or a new left bundle branch block, mandates immediate action: the patient is treated as having a heart attack on the strength of the ECG alone, without waiting for blood results.
Why cardiac markers lag behind the ECG
Troponin I or T and the CK-MB fraction are the routinely used cardiac markers, though lactate dehydrogenase and aspartate transaminase can also reflect myocardial damage. Their timing matters: CK-MB begins rising 2 to 4 hours after chest pain and peaks at 6 to 8 hours, while troponin may not be detectable until 6 to 8 hours after onset, and the earliest markers can stay undetectable for the first 6 to 12 hours. Testing too early can produce a falsely normal result, which is why Dr. Goel recommends serial testing at 4 to 6 hour intervals.
Where markers actually help
Cardiac markers have no role in deciding whether to give thrombolysis in ST-elevation MI. If the ECG shows ST elevation, the patient is thrombolyzed immediately rather than waiting for blood results to return. Their real value is in non-ST-elevation MI and unstable angina, where they are what separates the two: an elevated troponin or CK-MB means non-STEMI, and a normal result with a matching clinical picture means unstable angina.
The role of chest X-ray and echocardiography
A chest X-ray helps rule out conditions that can mimic acute coronary syndrome, particularly aortic dissection and pulmonary edema, which matters because thrombolysing a dissection can trigger sudden cardiac arrest. Echocardiography, Dr. Goel added, is now routine in suspected heart attacks at tertiary care centers alongside ECG and cardiac enzymes, since it can reveal regional wall motion abnormalities, valvular leaks or poor heart function that point toward an ongoing event.
This article is based on a Jivo Masterclass session conducted by Dr. Rohit Goel, Principal Consultant, Cardiology, Max Hospital, Gurgaon. The article has been summarised with the assistance of an AI tool from the original masterclass recording. Watch the full Masterclass recording
Looking for a cardiology consultation or a second opinion on ischemic heart disease? Get in touch with the Jivo team
This guide is based on a live Jivo Masterclass — Dr. Rohit Goel taught doctors across Africa on June 1, 2025.
FROM THE LIVE Q&A
Dr. Denawi
What is the prognosis of patients with ST-elevation MI if thrombolysis is not done, especially when there are contraindications?
Dr. Rohit Goel
The prognosis is poor when a patient with ST-elevation MI cannot be thrombolyzed because of a contraindication. Ideally these patients should be sent for primary angioplasty; if that is also unavailable, they should be managed medically in an ICU with aspirin, clopidogrel or ticagrelor, statins, beta blockers, ACE inhibitors, nitrates and heparin or low molecular weight heparin, using whatever resources are available. Outcomes can be described as roughly 50/50: some patients respond well to this treatment, while others deteriorate and need referral to a higher-level facility.
Frequently Asked Questions
What is the approach for aortic dissection presenting like acute coronary syndrome?▼
Management of aortic dissection depends on which part of the aorta is involved. If the dissection involves the ascending aorta or the arch, it needs surgical management. If it involves the descending thoracic aorta or the descending abdominal aorta, percutaneous repair of the aneurysm is possible instead.
What is the lag time between the onset of symptoms and ST elevation on ECG?▼
Once symptoms begin, the earliest ST elevation can appear on ECG within 15 to 30 minutes. This ST elevation persists if there is complete occlusion of the artery, and can still be present up to 48 hours later. If blood flow is restored spontaneously, whether from medicines or other reasons, the ST elevation resolves; otherwise it persists until the artery is reopened.
What is the mortality rate for patients with ST-elevation MI?▼
Mortality in ST-elevation MI can be quite high if the patient is not treated properly, up to 30 to 50%, which is why adequate and timely treatment matters so much. Cardiac echo, alongside ECG and cardiac enzymes, is very important and can pick up early signs of heart damage; it is now one of the first-line investigations at tertiary care hospitals in suspected cases.
Is cardiac ultrasound of no importance in ischemic heart disease, and could you give a summary of its management?▼
Cardiac echo is important and is now done routinely, alongside cardiac enzymes and ECG, in suspected cases of heart attack at every tertiary care hospital where it is available. In summary, once ischemic heart disease is confirmed, every patient is loaded with aspirin (325 mg) along with clopidogrel (300 mg), prasugrel (60 mg) or ticagrelor (180 mg), a statin (atorvastatin or rosuvastatin, 40 to 80 mg), a beta blocker if blood pressure and heart rate allow, and glyceryl trinitrate for pain relief alongside oxygen. From there, ST-elevation MI patients receive heparin ahead of primary angioplasty, or are thrombolyzed if angioplasty is unavailable; non-ST-elevation MI and unstable angina patients are managed medically with low molecular weight heparin or fondaparinux instead of thrombolysis, and are escalated to coronary angiography and angioplasty or bypass surgery if they are high-risk or not improving.
Can myocardial bridging cause acute coronary syndrome, or can it be a risk factor?▼
Myocardial bridging can cause chest pain and can act as a risk factor. The initial approach is medical management with beta blockers, calcium channel blockers or nitrates. If the patient's chest pain continues despite medication, the next step is bypass surgery rather than angioplasty, since angioplasty is not successful in a bridged segment of artery.
Should doctors wait for troponin results before treating a suspected STEMI?▼
No. If the ECG shows ST elevation or a new left bundle branch block, treatment should start immediately. Cardiac markers play no role in that decision and are only useful for distinguishing non-STEMI from unstable angina.
Why can a troponin test be falsely normal early in a heart attack?▼
Troponin may not be detectable for the first 6 to 8 hours after symptom onset, and CK-MB only starts rising after 2 to 4 hours, so testing too early can miss a real heart attack. Serial testing every 4 to 6 hours is recommended.
In This Series: Diagnosis and Management of Ischemic Heart Disease
- 1.Diagnosis and Management of Ischemic Heart Disease
- 2.Recognizing a Heart Attack: Classical and Atypical Symptoms of Acute Coronary Syndrome
- 3.ECG and Cardiac Biomarkers: The Two Investigations That Diagnose a Heart Attack
- 4.STEMI, Non-STEMI and Unstable Angina: How to Tell Them Apart
- 5.Emergency Drug Protocol for ST-Elevation Myocardial Infarction
- 6.Primary Angioplasty or Thrombolysis: Choosing the Right Reperfusion Strategy
- 7.Thrombolytic Drugs and When Thrombolysis Should Not Be Used
- 8.Managing Non-STEMI and Unstable Angina
- 9.Cardiac Rehabilitation, Follow-Up and Preventing the Next Heart Attack
- 10.Heart Attack Drugs in Pregnancy and Distinguishing Aortic Dissection from ACS