Have you or a loved one recently suffered from a STEMI (ST-elevation myocardial infarction) heart attack? Are you a physician or med student looking for STEMI diagnostic and treatment guidelines? This article is an all-encompassing STEMI resource guide.
Patient’s Guide to STEMI
What is a STEMI Heart Attack?
A STEMI is a full-blown heart attack caused by the complete blockage of a heart artery. A STEMI heart attack, like a Widow Maker, is taken very seriously and is a medical emergency that needs immediate attention. For this reason its often called a “CODE STEMI” or a “STEMI alert.” STEMI stands for ST elevation myocardial infarction. “ST elevation” refers to a particular pattern on an EKG heart tracing and “myocardial infarction” is the medical term for a heart attack. So STEMI is basically a heart attack with a particular EKG heart-tracing pattern.
When someone is being evaluated for chest pain the EKG tracing is done as soon as possible to help see if it’s the heart. An ST-elevation myocardial infarction (STEMI) is a combination of symptoms of chest pain and a specific STEMI EKG heart tracing. The EKG has to meet what is called STEMI criteria to make a correct diagnosis, just like an NSTEMI will provide another set of specific diagnostic criteria. The EKG also provides information as to which part of the heart the blocked artery is supplying, for example an anterior vs. a posterior STEMI vs. an inferior STEMI. An anterior STEMI is the front wall of the heart, and the most serious. A posterior STEMI is the back wall of the heart. An inferior STEMI is the bottom wall of the heart.
What Happens to the Heart?
In a heart attack there is sudden rupture of an unstable part of the wall in a heart artery. This leads to a build up of clot in an attempt to heal it however this clot formation results in total blockage of the artery. Unfortunately this total blockage leads to loss of blood supply to the heart beyond that point. The heart muscle stops working within minutes of this and dies within minutes to hours unless the artery can be opened back up. For this reason every minute from the onset of a heart attack is absolutely critical. Often the patient doesn’t make it to hospital due to sudden death. For those that leave it too long or for those in whom the heart attack isn’t treated, the heart muscle dies and is replaced by a non beating scar.
The most important part of any STEMI treatment protocol is to get to the hospital as quick as possible, so basically to call 911! In a STEMI an artery is blocked and treatment centers on opening this up as quick as possible. The preferred way to do this is by performing something known as angioplasty and stent placement. In this procedure the artery is opened back up working through a small tube passed to the heart either from the wrist or the groin. In some cases this cannot be performed fast enough and to avoid a delay in treatment clot busting drugs are used. Unfortunately these are not as good as they are less likely to open the artery back up and are also associated with bleeding complications. They are better than no treatment at all though so sometimes we have to use them.
In addition to this a number of other treatments are used. Painkillers such as morphine are used to settle pain and reduce the anxiety. Oxygen is administered to those who are breathless or have heart failure. EKG monitors are attached so that potentially lethal arrhythmias such as ventricular fibrillation or even less dangerous but still significant arrhythmias such as inappropriate sinus tachycardia or AFIB with RVR can be identified and treated. Blood thinners such as heparin, aspirin and other platelet inhibitors (clopidogrel/ticagrelor) are used to improve outcomes and prevent more heart attacks.
Educating patients and their families is one of the most critical aspects of care after a STEMI. Several new medicines are started after a heart attack, several of which may be needed lifelong. Patients need to be sure they take the medications prescribed to have a benefit. Stopping smoking is essential. It’s important patients follow up with their doctors. Drugs should be used to control blood pressure such as amlodipine if uncontrolled. After a STEMI patients will be enrolled in cardiac rehabilitation that is a program they attend on a regular basis. This involves exercise, addressing questions such as time of return to physical activities and dietary concerns. Following these things after the STEMI is arguably as important as treating the STEMI itself.
STEMI Guidelines for Healthcare Professionals
This section provides STEMI management guidelines for doctors and physicians that are compliant with AHA & ACC STEMI heart attack guidelines.
Identifying a STEMI with an EKG
The STEMI definition varies by sex and age.
For men ≥ 40 years old – 2mm in V2-V3 and 1mm in all other leads.
For men ≤ 40 years old – 2.5mm in V2-V3 and 1mm in all other leads.
For women – 1.5mm in V2-V3 and 1mm in all other leads.
A STEMI can be localized by identification of ST elevation in the following.
STEMI type EKG changes Likely Artery
Anterior STEMI – V3 V4 LAD
Inferior STEMI – II III AVF RCA >> Lcx
Posterior STEMI – STdepression V1 V2 V4 V4 RCA >> Lcx
Lateral STEMI – I AVL V5 V6 Lcx
Anterolateral STEMI – I AVL V3 V4 V5 V6 LAD / Lcx
Septal STEMI – V1 V2 LAD
Anteroseptal STEMI – V1 V2 V3 V4 LAD
LBBB and STEMI EKG
The baseline EKG in LBBB makes diagnosis of STEMI more challenging. Although not perfect, the Sgarbossa criteria are often applied. The points as seen below are added together and a total score of ≥ 3 has 90% specificity for diagnosing LBBB and STEMI.
- Concordant (Upward) ST elevation > 1mm in leads with a positive QRS complex (a score of 5)
- Concordant ST depression > 1 mm in V1-V3 (a score of 3)
- Excessively discordant ST elevation > 5 mm in leads with a negative QRS complex (a score of 2).
Risk Factors for ST-Elevation Myocardial Infarctions
Some scores have been developed to work out a STEMI patient’s risk of poor outcomes. These scores incorporate many factors that include the following:
- Older age
- Worsening heart failure
- Time taken to treat the STEMI
- Cardiac Arrest
- Earlobe Crease
- Fast heart rate
- Low blood pressure
- Kidney disease
We can use these scores to determine risk and how aggressive we should be in treating patients presenting with STEMI.
STEMI Protocol for Treatment
STEMI patients who present within 12 hours of symptom onset should receive treatment to try and open up the blockage known as reperfusion. This can either be by clot busting drugs given through the veins or by a procedure known as balloon angioplasty and stent placement (PCI). PCI is by far the preferred option as long as it can be done in time.
- If there is a possibility of PCI starting within 120 minutes (within 90 preferred, the faster the better) then this is preferred
- If there isn’t the possibility of being taken to a PCI center and the procedure started by 120 minutes then clot busting drugs should be given
- If its decided that clot busting drugs be used, then these should be given within 30 minutes
STEMI and Cardiac Arrest
- Patients with cardiac arrest caused by lethal heart rhythms should have initiation of a cooling hypothermia protocol
- Patients with cardiac arrest surviving to hospital and STEMI initially should have PCI
STEMI and Angiography after Lytics
- Those who got lytics but are in in shock, HF, or high-risk findings on testing should have angiography
- In those even with successful reperfusion therapy its reasonable to perform angiography prior to discharge, although not within 2-3 hours of lytic therapy
Medications After ST-Elevation Myocardial Infarction
Aspirin should be given for STEMI and continued life long
This includes Ticagrelor, Plavix and Prasugrel; this should be given early or at time of stent placement in STEMI. Should be given for a year if stent is placed.
Heparin After Lytics
Heparin should be given for at least 48 hours after lytic therapy and continued for the hospitalization or until PCI performed.
Beta-blockers should be given after STEMI in those patients without contraindications
It’s reasonable to use ACE inhibitors in all patients after STEMI without contraindications
Please share your experience in the comments for others to learn from.