ROSC, hypotension and an ECG exigency

Description

• SR 90/min (borderline for 1st degree heart block), normal axis.
• ST elevation in the inferior leads (II, III, aVF)
• ST elevation in V1, V2 and V3
• Reciprocal ST depression in lateral leads (I, aVL and V6)

Interpretation

• Inferior STEMI with right ventricular involvement, due to acute proximal occlusion of the right coronary artery.
• Haemodynamically unstable RV infarction is associated with high mortality.

Key features suggesting RV infarction are

• ST elevation in V1
• ST elevation in lead III > lead II

Note that about one quarter to one third of inferior STEMIs are associated with RV infarction, and nearly 90% of RV infarctions occur with coexistant inferior MI.

ST segment elevation in V1 should always make you suspect the presence of RV infarction.

The typical findings of RV infarction in V1 and V2 are:

• ST elevation in V1 exceeding the magnitude of ST elevation in V2
• ST segment in V1 is isoelectric and the ST segment in V2 is markedly depressed

These findings are not present in the ECG of our patient. Although ST elevation is usually restricted to lead V1 in RV infarction, it can occasionally extend across the precordial leads as shown in this ECG.

Repeat the ECG with right-sided precordial leads.

ST elevation in V4R confirms RV infarction, as shown in this repeat ECG:

The approach to management includes:

• Immediate activation of the cath lab.
• Employ a team-based approach to resuscitation in an appropriately equipped and staffed resuscitation area.
• Confirm ETT placement, adequacy of oxygenation (target SaO2 94-98%) and ventilation.
• Obtain large bore IV access and commence full non-invasive monitoring (SpO2, ETCO2, BP, ECG and temperature)
• Treat cardiogenic shock due to RV infarction:
  — 250 mL crystalloid boluses followed by reassessment (targeting adequate end organ perfusion, usually with MAP >65 mmHg)
  — maintain preload by avoiding nitrates and excessive intrathoracic pressures (e.g. avoid high PEEP)
  — maintain atrio-ventricular synchrony
  — transfer to the cath lab for cardiac catheterisation ASAP
• Commence supportive care of the intubated patient (e.g. FAST HUGS IN BED Please!)
• Commence Targeted Temperature Management (TTM) as appropriate

This patient’s presentation is consistent with a critical right coronary artery occlusion requiring emergent reperfusion therapy. Ideally, transfer to the cath lab should occur so rapidly that there is insufficient time to do much else!

If percutaneous coronary intervention (PCI) is not available, then thrombolysis — though not as effective, particularly in the presence of cardiogenic shock — should be performed. Following thrombolysis, transfer to a facility with a cath lab is still a priority (for rescue therapy and/or further investigation).

In addition to judicious fluid boluses (to improve preload and RV function), ongoing hypotension may be treated with catecholamine infusions (e.g. dobutamine, noradrenaline), levosimendin (a calcium sensitiser), and devices such as intra-aortic balloon pumps (LV dysfunction may result from the inferior STEMI component) until definitive treatment can be performed.