A posterior myocardial infarction can be difficult to see on a standard 12-lead ECG. In a patient being assessed for acute coronary syndrome (ACS), horizontal ST depression in leads V1–V3 may be a reciprocal clue to a posterior coronary occlusion—not reassurance that no heart attack is occurring. Clinicians may look for supporting ECG features and record posterior leads V7–V9 when suspicion persists. Anyone with possible heart attack symptoms should call emergency services immediately; do not wait for another ECG or try to diagnose the infarct location yourself.
When should clinicians suspect a posterior infarction?
Consider it when a patient has a presentation concerning for ACS and the standard 12-lead ECG shows horizontal ST-segment depression in V1–V3. These anterior leads can show reciprocal changes from injury on the posterior side of the heart, so the pattern can conceal rather than exclude an infarction. The 2023 European Society of Cardiology (ESC) guideline describes ST depression in V1–V3—especially with a positive terminal T wave—and/or ST elevation in V7–V9 as highly suggestive of posterior coronary occlusion, often involving the left circumflex artery. ESC 2023 acute coronary syndromes guideline.
As an Amazon Associate I earn from qualifying purchases.
Features that strengthen the ECG suspicion
- Horizontal ST depression in V1–V3.
- A dominant R wave in V2.
- Upright T waves in the anterior leads.
- A broad, prominent R wave.
- ST elevation on supplemental posterior leads V7–V9.
The ACC’s 2022 chest-pain pathway describes the dominant R wave in V2, upright anterior T waves, and a broad prominent R wave as supporting features. None should be interpreted in isolation: ECG findings belong alongside the clinical history, examination, and other testing. ACC 2022 emergency-department chest-pain consensus pathway.
Windows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallCrashes, No Sound, or Screen Glitches?
Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteWhat do posterior leads V7–V9 add?
V7–V9 record electrical activity from the posterior chest, providing views that the routine 12-lead tracing does not directly include. Clinicians can use them when posterior infarction remains a concern despite an inconclusive standard ECG, including ongoing symptoms with ST depression in V1–V3. The 2025 ACC/AHA acute coronary syndromes guideline and the ESC guideline discuss posterior leads in this context. 2025 ACC/AHA/ACEP/NAEMSP/SCAI acute coronary syndromes guideline.
#1 Best Overall
- Simple to Use Without a Subscription: No Bluetooth, Wi-Fi, cords or PC needed. Place the device near your smartphone. Monitor your heart by placing your fingers or thumbs on the silver KardiaMobile EKG sensors. Know in 30 seconds whether your heart rhythm is normal.
Placement and interpretation
The 2022 ACC pathway places V7 at the left posterior axillary line, V8 at the tip of the left scapula, and V9 in the left paraspinal region, all in the same horizontal plane as V6. In the posterior STEMI pattern it describes, ST elevation of at least 0.5 mm in one or more of V7–V9 is a confirming finding. That threshold is part of a clinical ECG pattern, not a stand-alone rule that replaces assessment of the complete tracing and patient.
How to interpret a normal or inconclusive first ECG
A normal or nondiagnostic initial ECG does not rule out ACS. The 2025 ACC/AHA guideline states: “The absence of electrocardiographic evidence of ischemia does not exclude ACS.” ECG changes can evolve; clinicians may repeat ECG assessment when symptoms persist or the patient’s condition changes. The guideline reports that a second and/or third ECG during EMS transport may identify up to 15% of additional STEMI cases not present on the first study. This figure concerns STEMI detection by serial prehospital ECGs generally, not posterior infarction specifically. 2025 ACC/AHA acute coronary syndromes guideline.
Rank #2
- Record and store ECG signals, and display heart rate for home health care use. There is no subscription or hidden cost required to use the device & app.
- The device can be connected with PC via USB, with mobile phone via Bluetooth.
- The function of software PC and mobile phone includes sample mode and time setting, upload case, case review, measurement etc.
- Powered by Built-in large capability rechargeable lithium battery.
- The device is intended for OTC (over-the-counter) Use. Implanted pacemaker are not recommended to use with this device. This device is not intended to substitute for a hospital diagnostic ECG device.
What symptoms warrant emergency help?
Symptoms can raise concern for a heart attack, but they cannot reliably identify which part of the heart is affected. Warning signs may include:
The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →- Chest pressure, squeezing, fullness, or pain.
- Discomfort in one or both arms, the back, neck, jaw, or stomach.
- Shortness of breath, cold sweat, nausea, lightheadedness, or unusual tiredness.
Symptoms vary between people and may be less obvious than chest pain. The American Heart Association advises calling 911 for possible heart attack warning signs. Outside the United States, call the local emergency number. Do not wait for symptoms to worsen, for a posterior-lead tracing, or for repeat testing before seeking emergency care. American Heart Association: Warning Signs of a Heart Attack.
Quick Recap
Rank #4
- CONFIDENCE IN EVERY READING: Monitor your heart health with the OMRON Complete 2-in-1 Upper Arm Blood Pressure Monitor's Advanced Accuracy Technology and EKG measurement; Store up to 90 readings to track your progress
- SAFEGUARD YOUR HEART: Get a more complete picture of your heart health by combining blood pressure and EKG measurements, helping you and your doctor determine if treatment or further evaluation is needed
- START YOUR DAY WITH CONFIDENCE: Increase the accuracy of your blood pressure readings with excessive Body Movement Detection alerts; Regular monitoring can reveal irregular fluctuations before they lead to serious complications
- TURN NUMBERS INTO INSIGHTS: Connect effortlessly to the free OMRON connect app via Bluetooth to store unlimited blood pressure readings, track trends, and share reports with your doctor; Compatible with Apple Health and Google Fit
- READY OUT OF THE BOX: Includes everything you need to start monitoring your heart health; OMRON blood pressure + EKG monitor, wide-range D-ring blood pressure cuff (fits arms 9"–17"), storage case, instruction manual, quick start guide and four AA batteries
Rank #3
- Accurate and detailed EKG results - Records a medical-grade, six-lead EKG and provides FDA-cleared determinations of your heart rhythm in just 30 seconds.
- Six Leads, Six Times more Information: Detects six of the most common arrhythmias including AFib, Bradycardia, Tachycardia, Sinus Rhythm with Premature Ventricular Contractions (PVCs), Sinus Rhythm with Supraventricular Ectopy (SVE), and Sinus Rhythm with Wide QRS.
- 6L Max includes one year of KardiaCare: Membership is required to use this 6-lead EKG. You will be prompted to enter payment details when you create your account, but you will not be charged during the first year. Your membership renews after one year unless canceled.
- Board-Certified Cardiologist EKG Reviews - KardiaCare includes four free EKG reviews per year, available to use anytime during the year. Using your detailed 6-lead EKG results, cardiologists can detect over 20 arrhythmias, with results delivered in just 24 hours. Additional reviews can be purchased for $39 each
- Automatically Email Your EKG to Doctors or Anyone - KardiaCare enables you to set up automatic emails so that results from your EKGs will be emailed to anyone you choose.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
