STEMI at Sea — When Minutes Matter and PCI Is Hours Away

Introduction: The Reality of STEMI at Sea

In an urban emergency department, ST-elevation myocardial infarction follows a well-rehearsed script. The patient presents with crushing chest pain. A 12-lead ECG is obtained within ten minutes. The cath lab is activated. Within 90 to 120 minutes of first medical contact, a balloon is inflated across the culprit lesion, and the occluded artery is open. Door-to-balloon time is measured, audited, displayed on hospital dashboards. The entire system is engineered around a single principle: time is myocardium.

Now place that same patient in a ship medical centre, 800 nautical miles from the nearest port with a cardiac catheterisation laboratory. The nearest helicopter is at the edge of its operational range. The sea state is Force 6. Your 12-lead ECG machine is bolted to a desk that is moving through three axes of motion. There is no interventional cardiologist. There is no cath lab. There is no possibility of primary percutaneous coronary intervention within 120 minutes — or within 12 hours. You are the entire cardiology department, and the therapeutic decisions you make in the next thirty minutes will determine whether this patient's left ventricle survives intact or whether they develop cardiogenic shock somewhere between here and the coast.

This article is a framework for managing STEMI in the maritime environment. It does not replace clinical guidelines. It translates them into the reality of a ship medical centre where the gap between guideline-recommended care and available resources is measured not in minutes but in days.

Recognition at Sea: ECG Interpretation in a Moving Medical Centre

The first challenge is diagnostic. Obtaining a clean 12-lead ECG on a moving vessel is a skill that hospital training does not teach. Ship motion introduces baseline wander and movement artefact that can obscure or mimic ST-segment changes. A rolling sea state generates rhythmic interference that corresponds to the vessel's period of roll, and this can produce pseudo-ST changes that trap the unwary clinician.

Practical measures to improve ECG quality at sea include securing the patient firmly to the examination couch, using additional skin preparation to reduce electrode impedance, applying electrodes during a period of relative stability if the patient's condition allows a brief wait, and running multiple tracings so you can compare them for consistency. An ST elevation that appears on one tracing but not on three consecutive ones is more likely artefact. An ST elevation that persists across multiple tracings, correlates with the patient's symptoms, and follows a recognisable coronary territory distribution is a STEMI until proven otherwise.

The diagnostic criteria remain the same as ashore. Look for ST elevation of at least 1 mm in two or more contiguous limb leads, or at least 2 mm in two or more contiguous precordial leads. New left bundle branch block in the context of ischaemic symptoms carries the same diagnostic weight. Reciprocal ST depression in mirror leads increases your diagnostic confidence significantly. Do not forget to check V7, V8, and V9 if you suspect a posterior STEMI — isolated ST depression in V1 to V3 with a compatible clinical picture should trigger a posterior lead ECG.

Common pitfalls at sea include misinterpreting motion artefact as atrial fibrillation, mistaking baseline wander for dynamic ST changes, and anchoring on a single ECG rather than serial tracings. The other trap is the patient who presents atypically: the elderly passenger with isolated dyspnoea and no chest pain, the diabetic crew member with epigastric discomfort and diaphoresis, the female patient with jaw pain and nausea. Maintain a high index of suspicion. At sea, the consequences of a missed STEMI are catastrophic because the window for correction is narrow and the distance to definitive care is vast.

The Decision Framework: Three Paths

Once you have confirmed a STEMI, you face a decision that no hospital emergency physician has to make: which therapeutic pathway is available to you, given your location, resources, and transit time to definitive care? The three paths are thrombolysis, conservative management with expedited evacuation, and immediate medevac without thrombolysis.

The decision depends on a matrix of factors:

1. Time from symptom onset. Thrombolysis is most effective within the first three hours. Benefit diminishes progressively and becomes marginal beyond 12 hours. If the patient has been having chest pain for 16 hours, thrombolysis is unlikely to help and the risk-benefit calculation shifts decisively.
2. Availability of thrombolytics. Does your medical centre carry tenecteplase, alteplase, or another thrombolytic agent? Many ship medical centres do not. If you do not have the drug, the decision is made for you.
3. Contraindications. Does the patient have absolute contraindications to thrombolysis? Active bleeding, recent surgery, history of haemorrhagic stroke, suspected aortic dissection, or a known bleeding disorder all eliminate this pathway.
4. Time to PCI. If a helicopter can reach you within two hours and deliver the patient to a PCI-capable hospital within three hours of first medical contact, primary PCI may still be achievable. Thrombolysis should not delay an evacuation that can deliver timely PCI.
5. Sea state and weather. A helicopter evacuation in Force 8 conditions may not be possible. If the weather window is closing, the decision to lyse becomes more urgent because the alternative pathway is blocked.

The framework, reduced to its essentials: if you are within three hours of symptom onset, you have the drug, there are no contraindications, and PCI is not achievable within 120 minutes of first medical contact, give thrombolysis. If PCI is achievable within that window, evacuate without lysing. If you are beyond the thrombolysis window and the patient is haemodynamically stable, manage conservatively and evacuate at the earliest opportunity. In every scenario, contact telemedical advice services early.

Thrombolysis at Sea: Practical Considerations

If you carry thrombolytics aboard and the decision is to lyse, the practical execution requires methodical preparation. This is not a procedure you will perform frequently. It may be the first and only time you administer a thrombolytic agent outside a hospital, and the environment does not forgive improvisation.

Tenecteplase is the preferred agent for maritime use because it is given as a single weight-adjusted intravenous bolus over five to ten seconds. There is no infusion to manage, no rate to titrate, and no pump required. The weight-based dosing is straightforward: less than 60 kg receives 30 mg, 60 to 69 kg receives 35 mg, 70 to 79 kg receives 40 mg, 80 to 89 kg receives 45 mg, and 90 kg or above receives 50 mg. A single bolus in a moving medical centre is vastly simpler and safer than managing a 90-minute alteplase infusion while the ship is rolling.

Alteplase, if tenecteplase is unavailable, requires a more complex protocol: a 15 mg intravenous bolus, followed by 0.75 mg/kg over 30 minutes (maximum 50 mg), then 0.5 mg/kg over 60 minutes (maximum 35 mg). This demands reliable intravenous access, an infusion pump or carefully calibrated drip rate, and 90 minutes of uninterrupted monitoring. On a moving vessel, the risk of infusion interruption or rate error is meaningful. If your ship carries alteplase but not tenecteplase, advocate to your medical superintendent for the switch.

Before administering either agent, complete the following checklist:

• Confirm the ECG diagnosis with serial tracings
• Document the time of symptom onset and time of drug administration
• Review all absolute and relative contraindications systematically
• Establish two reliable intravenous access sites — one for the thrombolytic, one for emergency medications
• Prepare for complications: have atropine drawn up for bradycardia (reperfusion arrhythmias), adrenaline available, and a defibrillator charged and at the bedside
• Weigh the patient accurately — do not estimate if weight-based dosing applies
• Administer adjunctive therapy: aspirin 300 mg (chewed), clopidogrel 300 mg loading dose, and enoxaparin per protocol unless contraindicated
• Inform the bridge that you have a critical patient and may need to request course diversion or helicopter evacuation

After thrombolysis, monitor continuously for signs of reperfusion: resolution of chest pain, reduction of ST elevation by more than 50% within 60 to 90 minutes, and reperfusion arrhythmias including accelerated idioventricular rhythm. Also monitor for complications, particularly bleeding. Check puncture sites. Ask about headache, visual changes, or any new neurological symptoms that could indicate intracranial haemorrhage. The most feared complication — intracranial bleeding — occurs in approximately 0.5 to 1% of patients and is often fatal at sea because neurosurgical intervention is unavailable.

Thrombolysis at sea is not a decision you make lightly. It is a decision you make because the alternative — hours of ongoing myocardial infarction without reperfusion — is worse.

Oxygen Management: The SpO2 Threshold

The reflexive administration of high-flow oxygen to every patient with chest pain is outdated practice and potentially harmful. The AVOID trial and subsequent guideline revisions have established that supplemental oxygen in normoxaemic STEMI patients does not improve outcomes and may increase infarct size through hyperoxia-mediated coronary vasoconstriction and increased oxidative stress.

The rule is clear: administer supplemental oxygen only if the patient's SpO2 falls below 94%. Target a saturation of 94 to 98%. Do not aim for 100%. If the patient is maintaining saturations above 94% on room air, leave the oxygen in the cylinder.

This matters doubly at sea because of the oxygen clock. Every litre of oxygen you use on a normoxaemic STEMI patient is a litre you will not have available if that patient later deteriorates into pulmonary oedema or if a second emergency arises. Use the oxygen burn-rate calculator to audit your supply the moment you start oxygen therapy, and titrate to the minimum flow rate that maintains the target saturation. At sea, evidence-based oxygen restraint is not just good medicine — it is good logistics.

If your patient does require oxygen — because of pulmonary oedema, cardiogenic shock, or hypoxaemia from any cause — integrate your oxygen planning into the overall medevac decision. A STEMI patient who needs 10 litres per minute of oxygen and is 40 hours from port presents a resource endurance problem that cannot be solved by clinical skill alone. It demands an operational conversation with the bridge.

Bridge Communication: SBAR-M for Cardiac Emergencies

The bridge needs to know about your STEMI patient, and they need to know in a format that supports operational decision-making. Clinical language does not translate. Telling the captain that your patient has "ST elevation in leads II, III, and aVF with reciprocal changes in I and aVL" communicates nothing actionable. You need to translate your clinical assessment into operational parameters that the bridge team can work with.

The SBAR-M framework — Situation, Background, Assessment, Recommendation, Maritime context — structures this communication. Use the SBAR-M template and adapt it to cardiac emergencies:

• Situation: "Captain, I have a 62-year-old male passenger with a confirmed heart attack. This is a time-critical emergency."
• Background: "Symptoms started approximately two hours ago. I have administered clot-dissolving medication. He is currently stable but at high risk of deterioration."
• Assessment: "This patient needs a hospital with a cardiac catheterisation laboratory within the next 12 to 24 hours. He could deteriorate suddenly and without warning. My oxygen supply will last approximately 18 hours at the current rate."
• Recommendation: "I recommend we request helicopter evacuation if available, or divert to the nearest port with a PCI-capable hospital. I need a decision on diversion within the next 30 minutes."
• Maritime context: "Current sea state, visibility, and weather conditions relevant to helicopter operations. Distance to nearest PCI-capable port. Alternative ports if primary is unreachable."

The critical phrase is "time-critical emergency." The bridge team understands urgency hierarchies. They understand that course diversions cost fuel, delay schedules, and generate commercial consequences. Your job is not to make the operational decision but to provide the medical assessment that enables the captain to make it. Be specific about timeframes. "As soon as possible" is not a timeframe. "Within 12 hours" is.

Medevac Decision-Making

The decision between helicopter evacuation and port diversion is not purely medical. It involves weather, distance, helicopter range, sea state, time of day, and the availability of receiving facilities ashore. The medevac decision-making framework provides a structured approach to this analysis, but for STEMI specifically, certain considerations dominate.

Helicopter evacuation is preferred when the vessel is within helicopter range (typically 150 to 250 nautical miles from a coast guard air station, depending on the aircraft type and weather), the sea state permits winching operations (generally up to Force 7, though this varies by service), the patient is stable enough to survive the transfer and flight, and the receiving hospital has PCI capability. Helicopter evacuation can deliver the patient to a cath lab within hours, potentially salvaging myocardium that would be lost during a 24-hour port diversion.

Port diversion is the fallback when helicopter evacuation is not possible. The key consideration is not simply the nearest port, but the nearest port with appropriate cardiac facilities. Diverting to a small island port with a 20-bed hospital and no catheterisation laboratory may get the patient ashore but does not get them to definitive care. Work with the bridge to identify PCI-capable hospitals along possible diversion routes. The company's maritime telemedical advisory service should assist with this, as they maintain databases of port medical facilities.

In either scenario, the patient must be packaged for transfer. This means stable intravenous access (secured and flushed), a clear and legible handover document, all medications administered and their times recorded, the ECGs printed and labelled, and the patient monitored during transfer. If using a helicopter, understand that the stretcher space is confined, monitoring equipment must be battery-operated, and the noise environment makes clinical reassessment during flight extremely difficult. The patient you hand over to the winchman must be as stable as you can make them.

Documentation: Medicolegal Protection and Handover

The documentation of a STEMI case at sea serves two purposes: medicolegal protection for you, and clinical handover for the receiving team. Both demand meticulous recording.

Your contemporaneous notes should include:

1. Timeline. Time of symptom onset (as reported by the patient), time you were called, time of first ECG, time of each subsequent ECG, time of drug administration, time of each communication with the bridge, time of each communication with telemedical services, time of medevac request, and time of patient transfer.
2. Clinical findings. Vital signs at regular intervals (at minimum every 15 minutes during the acute phase), ECG findings described in systematic terms, physical examination findings including lung auscultation and peripheral perfusion assessment, pain score trajectory, and any complications observed.
3. Decision rationale. Why you chose the therapeutic pathway you chose. If you gave thrombolysis, document that you reviewed contraindications and found none. If you withheld thrombolysis, document why. If you chose conservative management, explain the clinical reasoning. This is not defensive documentation — it is the record of your clinical thought process, and it protects you precisely because it demonstrates that you were thinking systematically.
4. Telemedical contact. Record the name and credentials of any telemedical physician you consulted, the advice given, and whether you followed or deviated from that advice (and why).
5. Resource constraints. Document your oxygen supply status, available medications, and any resource limitations that influenced your clinical decisions. A ship doctor who records that they titrated oxygen to the minimum effective flow rate because their total supply was limited to 14 hours has documented both good clinical practice and operational awareness.

Prepare a structured handover summary for the receiving medical team. This should be a single page that can be handed to the flight paramedic or ambulance crew and immediately understood. Include the patient's demographics, the working diagnosis, all medications given with doses and times, the current vital signs, the most recent ECG interpretation, ongoing infusions, allergies, and relevant past medical history. Print two copies — one to hand over, one to retain aboard.

Post-STEMI Monitoring Without Continuous Telemetry

Most ship medical centres do not have continuous cardiac telemetry. You have a 12-lead ECG machine, a pulse oximeter, a blood pressure cuff, and your clinical skills. This is enough, but it demands discipline in the monitoring schedule and vigilance for the complications that kill patients in the hours after a STEMI.

The threats in the post-STEMI period are arrhythmia, reinfarction, mechanical complications, and cardiogenic shock. Without telemetry, you cannot detect arrhythmias in real time. What you can do is maintain a high monitoring frequency and respond rapidly to any change.

• Vital signs every 15 minutes for the first two hours, then every 30 minutes for the next four hours, then hourly until evacuation or transfer. Any deviation from the trend — rising heart rate, falling blood pressure, new irregularity in the pulse, dropping saturations — triggers an immediate 12-lead ECG and clinical reassessment.
• Serial ECGs. Repeat the 12-lead ECG at 60 and 90 minutes after thrombolysis to assess reperfusion. Then repeat every two to four hours or whenever there is a clinical change. Compare each tracing to the previous ones. New ST changes, new Q waves, or new conduction abnormalities demand immediate action.
• Auscultation. Listen to the lungs at every vital signs check. New crackles suggest pulmonary oedema. Listen to the heart: a new murmur after STEMI may indicate papillary muscle rupture or ventricular septal defect — both surgical emergencies that fundamentally change the urgency of evacuation.
• Urine output. If you have a urinary catheter in place, monitor output hourly. Falling urine output is an early marker of cardiogenic shock and often precedes haemodynamic collapse by hours.
• Clinical reassessment. Engage with the patient regularly. Recurrence of chest pain may indicate reinfarction or failed reperfusion. New dyspnoea, new diaphoresis, new confusion, or new agitation are all red flags that demand immediate evaluation.

Keep the defibrillator at the bedside with pads attached and the device charged. Ventricular fibrillation can occur without warning in the post-STEMI period. The difference between survival and death may be measured in the seconds it takes to deliver the first shock.

Without telemetry, your monitoring plan is your telemetry. The frequency of your observations and your willingness to return to the bedside are the safety net this patient has.

The Wider Picture: Systems, Not Heroes

Managing a STEMI at sea is not about heroic individual performance. It is about having systems in place before the emergency arrives. The ship medical centre should have a STEMI protocol laminated and visible. The thrombolytic agent should be in stock, in date, and stored correctly. The ECG machine should be tested regularly. The bridge communication pathway should be rehearsed. The medevac request procedure should be familiar to both the medical team and the deck officers. The telemedical advisory service number should be on the wall, not buried in a file.

Every system failure that occurs during a STEMI at sea is a system failure that could have been prevented during a calm Tuesday in port. The time to audit your cardiac emergency capability is not when the patient is clutching their chest. It is during the routine medical centre inspection that you conduct every voyage. Check the drug expiry dates. Run a test ECG on a colleague. Walk through the medevac checklist. Call the bridge and confirm they know the procedure for a medical emergency course diversion. These are the investments that pay dividends at 0300 on a dark night in the North Atlantic.

STEMI at sea is the ultimate test of the ship doctor's dual identity: part clinician, part operational advisor. You must be good enough at cardiology to make the right therapeutic decision, and you must be good enough at maritime operations to ensure that decision translates into a pathway that gets the patient to definitive care alive. Neither skill alone is sufficient. Together, they are what maritime medicine demands.

References

1. O'Gara PT, Kushner FG, Ascheim DD, et al. 2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction. J Am Coll Cardiol. 2013;61(4):e78–e140. doi:10.1016/j.jacc.2012.11.019
2. Ibanez B, James S, Agewall S, et al. 2017 ESC Guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation. Eur Heart J. 2018;39(2):119–177. doi:10.1093/eurheartj/ehx393
3. Byrne RA, Rossello X, Coughlan JJ, et al. 2023 ESC Guidelines for the management of acute coronary syndromes. Eur Heart J. 2023;44(38):3720–3826. doi:10.1093/eurheartj/ehad191
4. Maritime and Coastguard Agency. The Ship Captain's Medical Guide. 23rd ed. London: The Stationery Office; 1999.
5. International Maritime Health Association (IMHA). Guidelines on Medical Equipment and Medicines on Board Ships. IMHA; 2023.
6. Stub D, Smith K, Bernard S, et al. Air Versus Oxygen in ST-Segment-Elevation Myocardial Infarction (AVOID Trial). Circulation. 2015;131(24):2143–2150. doi:10.1161/CIRCULATIONAHA.114.014494
7. Assessment of the Safety and Efficacy of a New Thrombolytic Regimen (ASSENT)-3 Investigators. Efficacy and safety of tenecteplase in combination with enoxaparin, abciximab, or unfractionated heparin. Lancet. 2001;358(9282):605–613.
8. International Maritime Organization. International Medical Guide for Ships. 3rd ed. Geneva: World Health Organization; 2007.

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