Electrocardiogram (ECG): What It Is, How It Works, and What It Detects

The electrocardiogram (ECG or EKG) is the most widely used cardiac study in the world. This quick, painless, and non-invasive test records the heart's electrical activity through electrodes placed on the skin, providing vital information about rhythm, heart rate, and potential structural abnormalities. At Dr. Elders Jimenez Iglesias's office in Hospital Galenia, Cancun, we perform 12-lead electrocardiograms with immediate interpretation by the specialist cardiologist.

What is an electrocardiogram and why is it important

An electrocardiogram is a diagnostic test that captures the electrical signals generated by the heart with each beat. Every cardiac contraction originates from an electrical impulse that travels through the heart from top to bottom, causing the atria and ventricles to contract in a coordinated manner to pump blood throughout the body. The ECG records these signals through 10 adhesive electrodes placed on the chest and limbs, producing a graphic tracing that the cardiologist analyzes to assess cardiac health.

This study is the cornerstone of any cardiological evaluation. It is the first tool the cardiologist uses when heart disease is suspected and is an essential part of every routine cardiac checkup, especially from age 40 onward.

How is an electrocardiogram performed step by step

The procedure is simple, fast, and completely painless. The patient lies on an examination table and exposes the chest, wrists, and ankles. The technician cleans the skin at contact points and places 10 adhesive electrodes: six at specific chest positions (precordial leads V1 through V6) and four on the limbs (one on each wrist and ankle). The patient remains still and breathes normally for approximately 10 seconds while the equipment records the electrical activity. Results are printed or displayed on a digital screen immediately.

What diseases and conditions does an ECG detect

• ●Cardiac arrhythmias such as atrial fibrillation, tachycardias, bradycardias, and atrioventricular blocks
• ●Acute myocardial infarction or signs of previous heart attack through ST segment changes and pathological Q waves
• ●Left or right ventricular hypertrophy, common in patients with chronic high blood pressure
• ●Electrical conduction abnormalities including bundle branch blocks, Wolff-Parkinson-White syndrome, and prolonged QT interval
• ●Acute pericarditis (inflammation of the pericardium) with diffuse ST segment elevation
• ●Effects of cardiac and anti-arrhythmic medications on the electrical tracing
• ●Electrolyte imbalances of potassium, calcium, or magnesium affecting heart rhythm
• ●Silent myocardial ischemia in patients with cardiovascular risk factors

When should you get an electrocardiogram

Your cardiologist may order an ECG in various clinical situations:

• ●Chest pain or pressure, with or without radiation to the arm or jaw
• ●Palpitations, racing heart, or sensation of irregular heartbeats
• ●Episodes of dizziness, vertigo, or fainting (syncope)
• ●Difficulty breathing during physical exertion or even at rest
• ●Annual routine cardiac checkup, recommended from age 40
• ●Monitoring and follow-up of hypertension, diabetes, or elevated cholesterol
• ●Preoperative evaluation before a scheduled surgery
• ●Monitoring response to medications that modify heart rhythm
• ●Sports evaluation for athletes beginning high-intensity training

Preparation for the electrocardiogram

Preparation is minimal. No fasting or medication changes are required unless specifically instructed by the cardiologist. Wear comfortable clothing that allows easy access to the chest and limbs, avoid applying creams or lotions to the chest on the day of the study (they interfere with electrode adhesion), and inform the doctor about all medications and supplements you currently take.

What do the ECG waves mean

The ECG tracing shows characteristic waves and segments that the cardiologist interprets systematically. The P wave represents atrial activation. The QRS complex reflects ventricular depolarization, and its amplitude indicates the condition of the ventricular muscle. The T wave corresponds to the electrical recovery of the ventricles. The PR interval measures conduction time between atria and ventricles, and the ST segment is critical for detecting ischemia or infarction, as its elevation or depression carries significant clinical meaning.

Advantages and limitations of the ECG

The electrocardiogram offers significant advantages: it is fast (less than one minute of recording), completely painless, uses no radiation, is affordable, and results are available instantly. However, it has the limitation of recording electrical activity at a single moment, so intermittent arrhythmias may go undetected. In those cases, the cardiologist supplements with 24-hour Holter monitoring. To evaluate heart structure and valve function, an echocardiogram is needed, and when coronary artery disease is suspected, a stress test or nuclear cardiology studies may be ordered.

ECG in Cancun: where to get one with a specialist

At Dr. Elders Jimenez Iglesias's office, located in Hospital Galenia, Office 403-A, Tower B, Hotel Zone in Cancun, we have state-of-the-art 12-lead digital electrocardiography equipment. The study is performed during the same cardiology consultation, and results are interpreted immediately. If you need an electrocardiogram in Cancun or are experiencing any cardiac symptoms, do not wait. Early detection of ECG abnormalities can prevent serious complications and save lives.

Dr. Elders Jimenez Iglesias

Cardiologist · Nuclear Cardiology

Professional License: 13819257 · Specialty: 12543211