Inferior/Right Ventricular Infarction

CLINICAL PRESENTATION AND TREATMENT

Lady Minto Hospital Emergency RoundsFebruary 2015

Prepared by Shane Barclay

Occurrence

Isolated Right Ventricular Myocardial Infarction (RVMI) is rare. More commonly occurs with inferior wall MI, occurring in 30-50 % of

such cases. Approximately 50% patients with RVMI have profound hemodynamic

and electrical complications. However long term outcomes are usually very good.

Clinical Presentation

RVMI: suspect in Inferior MI when patient presents also with:

1. Hypotension

2. Bradycardia

3. JVD

4. Clear chest sounds (no edema)

Right versus Left Ventricle

Oxygen demand is significantly lower in the Rt Ventricle because of smaller mass and lower afterload

Coronary perfusion in the Rt occurs in both systole and diastole

There is more extensive collateral circulation from left to right coronary arteries.

SA and AV node are supplied by arteries that also supply the Right Ventricle.

Hemodynamic consequences of RVMI

Right ventricular failure may cause limited filling pressures in the Rt Ventricle from decreased cardiac output, bi-ventricular failure or both.

Increasing Right Ventricular filling pressures (via fluid infusion) may cause shifting of the septum into the left ventricle which then impairs left ventricular filling and function.

Hemodynamic consequences of RVMI

Rt. Ventricular output may further be compromised by:

1. Hypoxemia from pulmonary edema

2. Alpha-adrenergic agonists

3. Mechanical ventilation with PEEP

Electrical Consequences – Inferior/RVMI

Bradycardia:

can arise from SA and AV node dysfunction Tachycardia and Ventricular Fibrillation

occur in up to 30% of patients

Treatment

Usual STEMI protocol, ie ASA, IVs, monitor TNKCautious use of Nitrates, beta blockers, diuretics,

opioids and bladder catheterization as these may impact preload, heart rate and contractility.

Treatment

If evidence of significant RV dysfunction or cardiogenic shock

1. IV fluid boluses, but try to limit to maximum 1 liter N/S

If still hypotensive/cardiogenic shock after one liter N/S 2. Pressors – Norepinephrine, Dobutamine

Treatment – Pressors

Norepinephrine

Start 0.03 mcg/kg/min IVDobutamine

Start 2 mcg/kg/min -titrate

Treatment – Analgesics

Fentanyl – Usually has minimal or no effect on BP and cardiac output.

May have some negative chronotropic effect (decrease HR) which if necessary can be treated with atropine.

Dose: 20-25 mcg IV aliquots

Treatment – Analgesics

Dose: mcg/hr

Rate: ml/hr

25 2.5

50 5

75 7.5

100 10

125 12.5

150 15

… …

Fentanyl Infusion:Admixture: Withdraw 20 ml from 100 ml minibag. Add 20 ml (1000 mcg) FentanylTotal Volume 100 ml.

Start by giving 25 mcg IV bolus and start infusion at 25 mcg/hr. If no response after 15 minutes repeat bolus and titrate up infusion rate

Treatment Summary Inferior MI IVs, monitor, labs, ECG 15 lead ECG TNK Have patient on Lifepak and have amp of Atropine handy If hypotensive, give small fluid boluses to maximum 1 liter If still hypotensive, consider norepinephrine drip – Start 0.03mcg/kg/min If still hypotensive, consider adding Dobutamine Start 2 mcg/kg/min Fentanyl for pain – 25 mcg and consider infusion.

Clinical Scenario

Clinical Scenario

54 year old male, previously completely healthy, presents with a history of waking with epigastric pain and burping. This increased in severity and is now “10/10” pain.

Vitals

BP 90/48 MAP 62HR 55/minRR 18Sats 95% on room air

Exam

Appears in acute distress, moaning and clutching his chest (i.e. real ‘man pain’.

Can answer questions and seems orientedHeart sounds are normalChest is clearJVD just under the ear lobe.

What are you going to do?

ECG

X-ray tech is coming, will be about 5 minutes.

Labs

Lab tech is taking labs, will be about 5-10 minutes.

Treatment Summary Inferior MI IVs, monitor, labs, ECG 15 lead ECG TNK Have patient on Lifepak and have amp of Atropine handy If hypotensive, give small fluid boluses to maximum 1 liter If still hypotensive, consider Norepinephrine drip – start 5-8

mcg/min If still hypotensive, consider adding Dobutamine Start 2 mcg/kg/min Fentanyl for pain – 25 mcg and consider infusion.