Article updated July 24, 2017
This case shows the value of serial EKGs in a patient with signs and symptoms of acute coronary syndrome. The recognition of ACS requires a thorough knowledge of not only the obvious signs, such as ST segment elevation, but also the easily overlooked EKG patterns highly suggestive of ischemic heart disease.
There are several noted fundamental limitations to the standard EKG. Awareness of these limitations can improve your ability to care for cardiac patients in an appropriate manner. These limitations include:
- Single brief sample. The standard EKG is a single snapshot look or sample of the ever-changing supply and demand picture of ischemic syndromes. In some cases, comparison between a new EKG and an older EKG are necessary to determine if there are changes.
- Lack of detection. The standard EKG does not accurately record all areas of the myocardium. The areas that the standard EKG is less sensitive for detection include the right ventricle, posterior basal walls and the lateral wall.
- Baseline patterns. Some patterns on the baseline EKG may make interpretation of ischemic changes difficult. These may include prior Q waves, left ventricular hypertrophy, bundle branch block and arrhythmias. Additionally, as the patient’s heart rate changes, so does each attribute of the entire QRS complex, from the p-wave through to the u-wave. Each signal’s vector, height and width, changes from beat to beat, although it is sometimes difficult to visualize.
- Interpretation. EKG waves may be difficult to interpret and cause disagreement among those reading it. Many studies have been conducted on the accuracy of EKG interpretation and have found inconsistencies at every skill level. These variations are reduced with experience.
- Clinical context. EKGs should not be read in a vacuum, but they should always be interpreted with the clinical picture in mind. Patients should be treated based on their symptoms even in the face of “negative EKG findings.” The EKG can be used to rule chest pain patients IN (i.e. STEMI), but cannot be used to rule them OUT (i.e. NSTEMI). The EKG should be included along with the history and physical examinations to identify those patients who appear to have high risk for acute ischemia.
The EKG Club experts created this case for these learning objectives:
- Basic: Identify acute coronary syndrome and appropriate initial treatment.
- Intermediate: Identify the EKG features that indicate the need for additional cardiac testing.
- Advanced: Identify and treat a symptomatic patient with T wave pseudo-normalization.
Patient Presentation: Male with history of MI
The patient is a 57-year-old male. EMS is called to his private residence in the early morning hours for a complaint of chest pain. He reports that he was awakened by mid retro-sternal chest discomfort. This discomfort reminded him of his prior MI five years ago. He reports that he had angioplasty and a stent was placed at that time and has been doing well ever since. He reports that when he awoke he also felt slightly short of breath, nauseated and sweaty.
Patient Assessment Findings
The patient is awake, alert, recognizes family members and is oriented to name, day, month, year and location. He appears to be in moderate distress, rubbing his chest with his hand. The patient is able to communicate verbally with you and is able to speak in complete sentences without significant respiratory distress. His skin is mildly diaphoretic, but is pink and warm.
The patient states that when he went to sleep earlier this evening he felt normal. He denies recent chest pain or exertional chest discomfort. He states that since his prior myocardial infarction, he hasn’t had to use any sublingual nitroglycerin for chest pain.
- Airway — Patent, no problems noted
- Breathing — Quiet respirations, no overt distress
- Circulation — Radial pulses present bilaterally, regular and strong
- Disability (Neuro) — Awake and alert, no focal deficits noted
- Exposure — No signs of trauma, no midline sternotomy scars noted
You quickly establish baseline vital signs and obtain a rhythm strip.
Here are the findings from your secondary assessment.
Patient’s vital signs:
Heart Rate: 88 bpm
Respiratory Rate: 18 rpm
Blood Pressure: 142/90 mm Hg
SpO2: 96 percent room air
Pain: 8/10
Patient’s past medical history:
Prior myocardial infarction with percutaneous coronary intervention and stents. Culprit vessel(s) not known to patient. Known hypertension. Known type II diabetes.
Allergies:
No known drug allergies
Meds:
Metoprolol
Enalapril
Glucophage
Aspirin
Simvastatin
You acquire a 12-lead EKG.
Initial EKG (click for larger image):
The computer generated interpretation is not available which makes it important to follow a standardized process for 12-lead EKG interpretation.
Answer these questions about the 12-lead EKG and the patient.
- Is there anything that concerns you about this EKG?
- Do his symptoms make you concerned about a possible acute coronary syndrome?
- Where would you like to transport this patient to?
Initial Treatment for Acute Coronary Syndrome:
Given the patient’s past history of myocardial infarction, hypertension, diabetes and high cholesterol (the latter syndrome inferred because of his medication list, even though he did not specifically mention it), you are appropriately concerned for a new acute coronary event. Your concern is especially heightened as the patient describes his current discomfort as being similar to his discomfort with his prior myocardial infarction.
You establish an IV saline lock on the first attempt and draw blood for the hospital. You perform a glucometer reading which shows a blood sugar of 110mg/dl (6.1 mmol/L). You give the patient four baby aspirin for a total dose of 325 mg and instruct the patient to chew and swallow them with a small sip of water.
You also begin to give the patient sublingual nitroglycerin in 0.4 mg doses. After the second dose of nitroglycerin, he reports that he is pain-free. During this time you have placed the patient on your cot and moved him to the ambulance and are en route to the nearest hospital which is 30 minutes away. The facility does have a cardiac catheterization lab “on call” at night. There is no cath lab staff on duty routinely at night, during holidays or on the weekends. It may take up to one hour for the cath team to arrive after activation.
Since he became pain-free after your initial interventions, you apply a transdermal nitroglycerin patch dosed at one inch (2.54 cm). You continue continuous rhythm strip monitoring. The patient remains in sinus rhythm.
Patient’s response to treatment:
After administration of aspirin and sublingual nitroglycerin, the patient reports that he is pain-free. He is no longer diaphoretic and reports that he feels much better. You are still 15 minutes from the hospital, so you repeat a 12-lead EKG.
Second EKG (click for larger image):
Once again, the computer generated interpretation is not available so follow a standardized process for 12-lead EKG interpretation.
- Is there anything that concerns you about this EKG?
- What is different about this EKG, taken when the patient was pain-free, compared to the first EKG when the patient was having chest pain?
- Does this change your destination?
- Does this change what you tell the receiving ER physician about the patient?
Patient follow-up: How to use T wave morphology to recognize NSTEMI
