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Complete atrioventricular block after return of spontaneous circulation in anterior ST-elevation myocardial infarction successfully bridged with transcutaneous pacing: a case report

This case report describes a 78-year-old man who survived an out-of-hospital cardiac arrest due to anterior STEMI and developed post-ROSC complete atrioventricular block, which was successfully managed with immediate prehospital transcutaneous pacing to stabilize hemodynamics until definitive hospital care could be provided.

Original authors: SALVATORE DI MARCO

Published 2026-07-27

📖 6 min read🧠 Deep dive

CC BY 4.0

Original authors: SALVATORE DI MARCO

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine your heart as a bustling city with a central power plant and a complex network of roads delivering electricity to every neighborhood. Sometimes, a sudden storm—like a blocked artery—cuts off power to a huge chunk of the city, causing the whole grid to crash. This is what happens during a heart attack, specifically a severe one called an anterior STEMI, where the main highway feeding the front of the heart gets clogged. When the city goes dark, the heart stops beating, leading to cardiac arrest.

But here's the tricky part: even if the emergency crews manage to restart the power plant and get the heart beating again (a moment called "Return of Spontaneous Circulation" or ROSC), the city isn't necessarily safe yet. The roads might still be damaged, or the traffic signals might be broken. In fact, the heart can suddenly develop a new problem where the signal from the top of the heart (the atria) can't get through to the bottom (the ventricles). It's like the mayor is shouting orders, but the messengers are stuck in a traffic jam, so the power plant only gets a tiny, slow trickle of commands. This is called a "complete atrioventricular block," and without a quick fix, the city goes dark again. This story is about a real-life emergency where doctors had to act fast to keep the lights on until the main road could be cleared.

The Story of the Heart's Traffic Jam

This case report tells the dramatic story of a 78-year-old man who suddenly collapsed while walking down the street. It was a witnessed cardiac arrest, meaning people saw him go down and immediately started chest compressions while waiting for help. When the advanced medical team arrived about 11 minutes later, the man's heart was in a state of "asystole"—a flatline, like a city with zero power.

The team sprang into action, performing high-quality CPR, intubating his airway, and giving him adrenaline to try to jumpstart his heart. About six minutes into their efforts, his heart rhythm changed from a flatline to a chaotic, quivering mess called ventricular fibrillation. They zapped it with a 200-Joule shock (a strong electric jolt) and kept pumping. Finally, after a total of 17 minutes of intense effort, the man's heart started beating on its own again. He had achieved ROSC.

At first, everything looked promising. The team checked his heart with a 12-lead ECG (a map of the heart's electrical activity) and saw signs of a massive heart attack in the front part of his heart (anterior STEMI). They prepared to rush him to the hospital to unblock the artery. But then, about 8 minutes after his heart restarted, things went wrong again.

His heart rate began to plummet. The map of his heart showed a terrifying new problem: a complete atrioventricular block. Imagine the heart's electrical system as a two-story building. The top floor (atria) was sending signals at a normal speed of about 85 beats per minute. But the bottom floor (ventricles), which actually pumps the blood, was completely disconnected. It was trying to run on its own backup generator, but that generator was sputtering along at a dangerously slow 18 beats per minute. The man's blood pressure was dropping, and his body was running out of oxygen.

The Lifesaving Bridge

The medical team realized that giving more adrenaline or drugs like atropine (which usually helps speed up a slow heart) probably wouldn't work. Why? Because the block wasn't just a "traffic jam" caused by a nervous system glitch; it was a physical breakdown of the heart's wiring due to the massive heart attack. The "wires" connecting the top and bottom floors were damaged by the lack of oxygen.

Instead of waiting for a drug to fix a broken wire, the team decided to build a temporary bridge. They used transcutaneous pacing. Think of this as an external remote control for the heart. They placed sticky pads on the man's chest and sent electrical pulses through his skin to force the bottom floor of the heart to beat. They set the remote to fire at 85 beats per minute, matching the speed of the top floor.

It worked almost instantly. The heart's electrical signals were captured by the external pulses, and the man's heart started pumping effectively again. His blood pressure stabilized at 125/74 mmHg, his oxygen levels improved, and his pupils (which had been unresponsive) started reacting to light again. The team kept the pacing going like a safety net while they drove him to the hospital for the real fix: opening the blocked artery.

What This Tells Us

This paper doesn't claim to have discovered a new disease or a magic cure. Instead, it highlights a critical lesson for emergency doctors: Just because the heart starts beating again doesn't mean the patient is safe.

The authors suggest that in cases of severe front-of-the-heart attacks (anterior STEMI), a sudden heart block is a sign that the damage is deep and severe. It's not a minor glitch; it's a major structural failure. The paper argues that in these specific, unstable situations, waiting for drugs to work might be too slow. The heart is too damaged to respond to chemical signals.

The key finding is that transcutaneous pacing can act as a vital "bridge." It doesn't fix the heart attack itself, but it keeps the patient alive and stable long enough to get to the hospital for the definitive treatment. The paper emphasizes that doctors need to watch the heart's rhythm, blood pressure, and carbon dioxide levels (a sign of how well blood is flowing) constantly after a patient is revived. If they see the heart slowing down and the signals getting disconnected, they need to act fast with electrical pacing rather than sticking to a standard "wait and see" approach with medications.

In short, this case shows that when a heart is struggling to survive a massive attack, sometimes the best way to keep it going is to take the controls manually until the real repair crew can arrive.

Technical Summary: Complete Atrioventricular Block After ROSC in Anterior STEMI Bridged with Transcutaneous Pacing

Problem Statement
Out-of-hospital cardiac arrest (OHCA) caused by acute coronary occlusion is a time-critical emergency where survival depends on rapid recognition of the underlying cause and timely transfer for definitive treatment. While complete atrioventricular block (CAVB) is a known complication of inferior myocardial infarction, it is less frequent in anterior ST-elevation myocardial infarction (STEMI). However, when CAVB occurs in the context of an anterior STEMI, it typically signifies extensive ischemic injury to the interventricular septum and the His-Purkinje conduction system. This specific pathophysiology is associated with severe hemodynamic instability, cardiogenic shock, and poor prognosis. A critical gap exists in the prehospital literature regarding the management of patients who achieve return of spontaneous circulation (ROSC) but subsequently deteriorate rapidly due to post-ROSC CAVB in the setting of an anterior STEMI. Standard algorithms for symptomatic bradycardia often prioritize pharmacological intervention (e.g., atropine), which may be ineffective or insufficient for infranodal blocks caused by extensive ischemia.

Methodology
This study presents a single case report of a 78-year-old male who suffered a witnessed OHCA while walking. The patient was managed by a physician-staffed advanced life support (ALS) team. The clinical sequence involved:

Initial Resuscitation: The patient presented in asystole. ALS protocols were initiated, including endotracheal intubation, high-quality chest compressions, and intravenous adrenaline (2 mg total). The rhythm converted to ventricular fibrillation, requiring a single 200-J biphasic defibrillation shock.
ROSC and Diagnosis: ROSC was achieved after 17 minutes of CPR. Immediate 12-lead electrocardiography (ECG) revealed extensive anterior STEMI.
Post-ROSC Deterioration: Approximately 8 minutes after ROSC, the patient experienced rapid hemodynamic collapse. Continuous multiparametric monitoring (ZOLL X Series) detected a shift to complete AV block with atrioventricular dissociation (atrial rate ~85 bpm, ventricular escape rhythm ~18 bpm), accompanied by falling blood pressure and end-tidal carbon dioxide (ETCO2).
Intervention: Based on the pathophysiology (suspected infranodal block due to anterior STEMI) and the failure of prior pharmacological support, the team bypassed further pharmacological escalation (atropine) and immediately initiated transcutaneous pacing. Pacing was set at 85 bpm, with output titrated from 180 mA to a capture threshold of ~80 mA.
Outcome: The patient was stabilized and transported to a hospital for definitive coronary reperfusion.

Note: The authors explicitly state that original ECG tracings, monitor screenshots, laboratory results, and angiographic images were unavailable at the time of manuscript preparation. The report relies on documented clinical observations, vital parameters, and the recorded therapeutic sequence.

Key Contributions and Results

Clinical Sequence: The report documents a rare and critical sequence: OHCA $\rightarrow$ ROSC via ALS $\rightarrow$ Immediate diagnosis of anterior STEMI $\rightarrow$ Rapid post-ROSC deterioration due to CAVB $\rightarrow$ Successful stabilization via transcutaneous pacing.
Hemodynamic Stabilization: Immediate transcutaneous pacing restored effective ventricular activation, stabilizing the heart rate at 85 bpm, blood pressure at approximately 125/74 mmHg, and ETCO2 levels, indicating the restoration of effective cardiac output.
Diagnostic Utility: The case demonstrates the utility of continuous ETCO2 and hemodynamic monitoring in the prehospital setting. A sudden decrease in ETCO2 and blood pressure, despite stable ventilation, served as an early indicator of deteriorating cardiac output and conduction failure before the patient became pulseless again.
Therapeutic Decision-Making: The authors detail the rationale for choosing electrical support over pharmacological agents. Given the anterior location of the STEMI and the nature of the block (likely infranodal), the probability of atropine reversing the conduction failure was deemed low. Transcutaneous pacing provided the necessary "bridge" to maintain perfusion during transport.

Significance and Claims
The paper asserts that ROSC should not be viewed as the endpoint of critical care but rather as the beginning of a dynamic phase requiring continuous reassessment. The primary educational message is that in anterior STEMI complicated by unstable CAVB, prehospital transcutaneous pacing can serve as a life-saving bridge to definitive coronary reperfusion.

The authors emphasize three practical learning points for emergency clinicians:

Continuous Reassessment: Apparent stabilization after ROSC must be followed by continuous monitoring of ECG, ETCO2, and hemodynamics to detect early recurrent deterioration.
Pathophysiological Interpretation: In anterior STEMI, advanced conduction disturbances should be interpreted as markers of extensive ischemia and potential hemodynamic collapse, rather than simple bradycardia.
Integrated Decision-Making: Clinical reasoning in unstable post-ROSC patients should integrate rhythm diagnosis, hemodynamics, and capnography to guide treatment, rather than relying solely on static algorithmic steps or heart rate alone.

The report concludes that while transvenous pacing may offer better tolerance for prolonged use, transcutaneous pacing is the most appropriate immediate intervention in the prehospital setting to restore effective ventricular activation and maintain circulation while arranging urgent coronary reperfusion. The authors maintain a modest tone, noting that the case illustrates the application of existing guidelines to a complex physiological scenario rather than proposing new algorithms or claiming definitive cures for the underlying ischemia.

The Story of the Heart's Traffic Jam

The Lifesaving Bridge

What This Tells Us

Technical Summary: Complete Atrioventricular Block After ROSC in Anterior STEMI Bridged with Transcutaneous Pacing

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