Chest pain in the primary care setting

Chest pain is a frequently encountered symptom in the primary care setting. Distinguishing an acute coronary syndrome (ACS) from more benign aetiologies can be challenging, even for an experienced cardiologist. Thus, a conservative approach, particularly for those patients considered at a higher risk of an ACS, is preferable. The early performance of a 12-lead electrocardiogram (ECG) can assist in risk stratifying these patients and determine the safest and most appropriate treatment strategy. In clinical situations where an ACS is considered a possible diagnosis and an alternate explanation for chest pain cannot be identified, rapid admission to a Coronary Care Unit (CCU) is essential.

Dr HN, a fifty-three year old academic professor, presented to his regular GP after experiencing a ten minute episode of chest discomfort whilst washing dishes with his family after dinner on the previous evening. His symptoms were indigestion-like but he had no previous history of gastro-oesophageal disease. Dr HN had well-controlled mild systemic hypertension (treated with telmisartan) but no dyslipidaemia nor diabetes mellitus and was a lifelong non-smoker. There was no family history of ischaemic heart disease (IHD) in direct relatives.

Dr HN was painfree at the time of seeing his GP. Nevertheless his GP performed a 12-lead ECG (Fig 1) which demonstrated subtle ST-segment depression in the inferior (II, III & aVF) and chest leads.

Figure 1 - ECG

       Fig 1 ECG

Dr HN’s GP contacted me directly by phone and immediately faxed the ECG for my assessment. After discussing Dr HN’s clinical presentation, we decided to admit Dr HN directly to Epworth Freemasons’ CCU. Upon arrival, a repeat ECG confirmed persisting subtle ST-segment depression. Initial, and subsequent, high-sensitivity troponin levels fell within the normal range. A chest x-ray was unremarkable. An echocardiogram (cardiac ultrasound) demonstrated normal left ventricular systolic function with no regional wall motion abnormalities. Furthermore, there were no echocardiographic features of pericarditis nor thoracic aorta pathology ie aortic dissection.

On the following day, Dr HN underwent a coronary CT angiogram (CCTA, or cardiac CT) to directly assess his coronary arteries prior to discharge. The absence of an elevated troponin level implied that a myocardial infarction had not occurred, however unstable angina was still a possibility. 50mg of metoprolol was required to ensure his heart rate was slow enough (ie. under 60 beats/minute) to optimise study quality. Within a single breath-hold, CT scanning of the entire heart was completed, timed to coincide with maximal intravenous contrast within the coronary arteries.

Analysis of the CCTA images revealed an obstructive (95% stenotic) cholesterol-rich plaque located within the mid-Right Coronary Artery (Fig 2). The remaining coronary arteries were plaque-free.

Figure 2 - Coronary CT angiogram

                    Fig 2 Coronary CT angiogram    

Dr HN underwent invasive coronary angiography via a radial artery approach at Epworth Richmond which confirmed the presence of this significant stenosis (Fig 3) and then enabled uncomplicated stenting of the lesion with a drug-eluting stent (DES). Dr NH was discharged the following day on dual anti-platelet therapy, along with a high-dose statin agent and his regular dose of telmisartan. Several months have elapsed and Dr NH has experienced no further chest pain.

Figure 3 - Invasive coronary angiogram

                 Fig 3 Invasive coronary angiogram

This case demonstrates several key points for the management of chest pain.

  1. Early performance of an ECG in the primary care setting enables early diagnosis of an ACS and assists with risk stratification
  2. Avoid ordering an outpatient troponin measurement – a normal level can be falsely reassuring while a delay in receiving an elevated troponin result will be deleterious to your patient
  3. Early inpatient admission to a CCU provides a safe, rapid and streamlined management approach for ACS
  4. Performance of an inpatient cardiac diagnostic test (eg CCTA, stress echocardiography) to accurately assess coronary arteries prior to discharge will establish the correct diagnosis and facilitate delivery of appropriate therapy, in this case a percutaneous coronary intervention (PCI)
  5. Consider other red flags as causes of acute chest pain – for example, aortic dissection, acute pericarditis, pulmonary embolism and pneumothorax.

Cardiology services, such as those provided at Epworth Freemasons, possess CCTA, stress echocardiography and nuclear myocardial perfusion testing. Each modality has specific advantages and disadvantages:

  • CCTA directly visualises coronary arteries and has a high negative predictive value for excluding obstructive coronary artery disease. Medicare subsidisation of this test requires referral by a specialist and most CT scanners require a slow and regular heart rate. Heavy coronary artery calcification can reduce the accuracy of stenosis assessment. Radiation doses are progressively lowering
  • Stress echocardiography provides both a functional evaluation of myocardial perfusion and additional data about cardiac structure and function (including ejection fraction, valvular function, aortic and pericardial pathology). Image quality (and thus sensitivity for identifying ACS) may be reduced in patients with increased BMI
  • Nuclear myocardial perfusion testing is also a functional study of myocardial oxygen delivery and requires intravenous injection of a radioactive tracer. Radiation dosages are significantly higher than those associated with CTCA. Overall accuracy for assessing obstructive coronary artery disease is similar to stress echocardiography, however less information about cardiac structure and function is obtained.

The role of ECG stress testing without imaging remains uncertain. Both the sensitivity and specificity of ECG stress testing for the diagnosis of obstructive coronary artery disease is markedly lower than CTCA or stress testing with imaging and such testing cannot be performed on patients with certain ECG abnormalities at baseline.

In summary, the management of chest pain in the primary care setting requires a rapid assessment and early referral to a medical centre with a comprehensive cardiology service should an ACS be a possibility.

References:
On request


Andris EllimsAUTHOR | Dr Andris Ellims
Dr Andris Ellims is a general cardiologist and cardiac imaging specialist incl echocardiography, CT and MRI. His PhD involved the use of cardiac imaging to evaluate cardiomyopathies. Find out more about the direct admisson pathway at Epworth Freemasons.
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PH | 03 9519 6512  WEB | www.victoriaheart.com.au

 

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