A 66-Year-Old Woman with Intermittent Chest Pain and Dyspnea Who Underwent Continued ST-Segment Monitoring to Identify Occult ST-Segment Elevation that Expedited Coronary Angiography and Revascularization

Background

A key symptom of acute coronary syndrome (ACS) is acute chest discomfort, which typically is described by the patient as pain, pressure, tightness, or burning [1]. Together with the patient’s medical history, an electrocardiogram (ECG) is one of the cornerstones in the diagnostic workup of acute coronary syndrome (ACS). ST-segment elevation myocardial infarction (STEMI), in contrast to non-ST-segment elevation ACS (NSTEACS), is defined by persistent ST-segment elevations in the ECG. NSTE-ACS is categorized as unstable angina in the absence of increased troponin levels, or as non-ST-segment elevation myocardial infarction (NSTEMI).

When the first ECG in a patient suspected for acute coronary syndrome is without ST-segment elevations, it is recommended to either perform sequential conventional 12-lead ECGs or to continuously monitor the ST-segment to identify new or intermittent ST-elevations [1,2]. Continuous ST-segment monitoring is not routinely used in patients admitted with symptoms suggestive of NSTE-ACS, in contrast to the continuous monitoring for arrhythmias.

Case Report

A 66-year-old woman was admitted to the hospital because of retrosternal chest pain. Her cardiovascular family history included a father with an unspecified heart condition. Modifiable cardiovascular risk factors included obesity (body mass index of 38.5 kg/m2), active smoking since the age of 10 years (50 pack-years), and untreated hypercholesterolemia. Her medical history included universal muscle and joint pain. She self-administered tablets of paracetamol, ibuprofen, oxycodone, and oxazepam. The extent to which the patient took non-aspirin non-steroidal anti-inflammatory drugs in the weeks leading up to her hospital admission was unclear.

The patient had several instances of dyspnea and chest pain during the previous 6 weeks, typically lasting 2 to 5 min, with a maximum of 10 min, and often in relation to physical activity and at night-time. She characterized the chest pain as a pressing and squeezing sensation with radiation to the right arm and the center of the neck, which was typically accompanied with dyspnea. The pain and dyspnea disappeared when the patient was at rest. Her general practitioner had prescribed a proton-pump inhibitor without effect, and after a couple of weeks, the pain had become more frequent and sometimes appeared at rest. Her general practitioner admitted her to the hospital on the suspicion of ACS. Upon admission, she had a slight pressing pain which soon spontaneously resolved.

A physical examination upon admission was normal, apart from a muffled sound on the right side of the chest. A chest X-ray showed no pathology. The initial conventional 12-lead ECG showed a sinus rhythm of 80 beats per min, without signs of ischemia (Figure 1). A normal echocardiographic examination was performed. Laboratory blood examination showed hypercholesterolemia with total P-cholesterol of 6.8 mmol/L and low-density lipoprotein of 4.1 mmol/L. At admission, the high-sensitivity cardiac troponin I level was normal (99 percentile <24 ng/L) at 14 ng/L, and was 12 ng/L after 3 h. The creatine kinase MB (CK-MB) level (reference value <4 µg/l) was stable but elevated at 7.6 µg/L and 7.3 µg/L, respectively.

As the conventional ECG showed no signs of ischemia, and high-sensitivity cardiac troponin I levels were also normal, the treating physician had no strong clinical suspicion of ACS. An ambulatory follow-up with coronary computed tomography (CT) angiography was therefore planned, to rule out underlying chronic coronary artery disease. The patient remained admitted over night for rhythm and continuous ST-segment monitoring with a 5-electrode vector-based ECG, EASI system (Philips IntelliVue central monitoring system information center iX, Andover, MA, USA). For continued monitoring of the ST-segment, the ST index was used. The ST index is the sum of the absolute value of the ST-segment in leads V2, V5, and aVF.

The patient had no discomfort, chest pain, or dyspnea during the continuous ST-segment monitoring. However, between the time of admission at 3: 00 p.m. and 7: 00 a.m. the following day, 10 spikes on the ST index were observed. At 7: 00 a.m., 1 additional set of cardiac markers, troponin I and CK-MB, remained unchanged to the first 2 sets. Between 7: 00 a.m. and noon, an additional 8 spikes were observed. On the derived 12-lead ECG, there were ST-elevations in leads II, III, and aVF and ST depression in leads V2 and V3 (Figures 2, 3). The patient was therefore referred for an acute coronary angiography on the indication of STEMI. After immediate transfer to the nearest cardiac center, coronary catheterization was pre-formed and showed a significant stenosis on the second segments of the right coronary artery. Stent implantation and revascularization were performed (Figure 4). The patient was discharged the following day without any symptoms.

After discharge, the patient participated in a rehabilitation program but declined the offered smoking cessation guidance. After completion of the rehabilitation program, she reported no chest pain or dyspnea. Today, 3 years later, she has no symptoms.

Discussion

The rhythm and continuous ST-segment monitoring system used was an EASI system. The EASI system is a 5-electrode vector-based system from which a 12-lead ECG can be generated [3]. The EASI system’s ECG has been compared to a conventional 12-lead ECG and found to be equal in diagnosing arrhythmia and ST-segment changes in patients with chest pain or ACS [4–6]. The ST index has been developed by Philips Medical Systems (Andover, MA, USA) to give a single value for continued monitoring of the ST-segments and for detecting ST-segment dynamics. The leads are chosen as they represent different areas of the heart: anterior (V2), lateral (V5) and inferior (aVF).

For patients presenting with suspected STEMI, the guidelines of the European Society of Cardiology stress the need for repeated conventional 12-lead ECG or monitoring of the ST-segment to capture intermittent ST-elevations [2]. Continuous ST-segment monitoring is not mentioned in the guidelines of the American College of Cardiology for the management of STEMI or in international guidelines for NSTE-ACS [1,7,8]. Recognizing the development of ST-segment elevations in patients suspected of NSTE-ACS is important, as the degree of myocardial infarction may be reduced by an acute percutaneous coronary intervention [1]. Continuous ST-segment monitoring may therefore be considered in all patients admitted under the suspicion for ACS and continued until the suspicion is dropped or the patient has received a coronary angiography.

Retrospectively, the current patient may also have had an element of vasospastic angina. Vasospastic angina is due to coronary artery spasm and characterized by episodes of angina at rest that typically respond well to short-acting nitrates [9]. Management of vasospastic angina includes smoking cessation and vasodilators. Supporting the suspicion of vasospastic angina, the patient fulfilled some of the Coronary Artery Vasospastic Disorders Summit diagnostic criteria for vaso-spastic angina: angina at night-time and transient ischemic ECG changes, as seen on the continuous ST-segment monitoring [9]. However, this patient’s primary symptoms were chest pain and dyspnea during physical activity, and significant coronary artery disease was detected and treated as the result of continuous ST-segment monitoring.

Conclusions

Continued ST-segment monitoring aids in identifying intermittent ST-segment elevations in patients admitted on the suspicion for ACS and thereby aids in identifying the need of an acute coronary angiography.