Non-Invasive Tests for Acute Coronary

SyndromeRebekah Crawford

March 2016

A little over 50 years ago, my father had a heart attack. He was driven to the hospital by friends after having “indigestion” for 2 days. He spent 2 weeks as an inpatient on an unmonitored rehabilitation ward and was treated principally with warfarin and digitalis. He was lucky and survived, but in that era, more than 20% of patients with an acute myocardial infarction died.

Vevrotec 2008

By the late 1960s, cardiovascular disease accounted for a 56% of all deaths. Steady decline to 30% of all deaths in 2013.

Coronary heart disease is the leading cause of death in Australian men and women

Kills 54 Australians each day, or one Australian every 27 minutes

Heart Foundation, Australia

Overview

Chest pain pathway Risk stratification Non-invasive cardiac investigations

TIMI score

Age ≥ 65 Aspirin use in the last 7 days At least 2 episodes of angina within the last 24hrs ST changes of at least 0.5mm in contiguous leads Elevated serum cardiac biomarkers Known Coronary Artery Disease At least 3 risk factors for CAD"The TIMI Risk Score for Unstable Angina/Non–ST Elevation MI", JAMA, 2000

% risk at 14 days of: all-cause mortality, new or recurrent MI, or severe recurrent ischemia requiring urgent revascularization

Score of 0-1 = 4.7% risk Score of 2 = 8.3% risk Score of 3 = 13.2% risk Score of 4 = 19.9% risk Score of 5 = 26.2% risk Score of 6-7 = at least 40.9% risk

HEART score

History ECG Age Risk factors Troponin

A prospective validation of the HEART score for chest pain patients at the emergency department. Int J Cardio 2013

Treadmill Stress Electrocardiography Patient selection criteria

- Able to exercise- ECG: No ST changes / arrhythmia

- Negative cardiac injury markers Procedure

- Bruce or modified Bruce protocol End points

- Symptom-limited- Ischemia

Result- Positive: 0.10 mV of horizontal ST-segment depression

- Negative: No exercise-induced abnormalities at 85% MPHR - Nondiagnostic: unable to reach 85% MPHR

Recommended within 72hrs of discharge Pts recommended to be started on precautionary

medical therapy while waiting for stress test 1

Cost-effective Need to be able to exercise Doesn’t identify pts with ACS missed by enzyme

testing2

Lowest sensitivity of all stress tests: risk of false negative test1. Testing of Low-Risk Patients Presenting to the Emergency Department With Chest Pain A Scientific Statement From the American Heart Association, Circulation. 2010 2. Immediate exercise testing to evaluate low-risk patients presenting to the emergency department with chest pain J Am Coll Cardiol. 2002

Stress ECHO Appropriate for patients with an intermediate pre-test

probability of CAD, no dynamic ECG changes and negative serial cardiac enzymes

Allows assessment of exercise capacity, structure and function of heart

Better sensitivity than exercise ECG (85% vs 43%) but similar specificity (95%) 1

Helpful for patients who can’t exercise Good positive predictive value

1. Assessment of patients with low-risk chest pain in the emergency department: Head-to-head comparison of exercise stress echocardiography and exercise myocardial SPECT. Heart J. 20052. Prognostic value of predischarge dobutamine stress echocardiography in chest pain patients with a negative cardiac troponin T. J Am Coll Cardiol. 2003

Myocardial Perfusion Imaging For patients with possible ACS, with no ECG changes,

negative initial troponin and ongoing (or recent) chest pain

Stress myocardial perfusion scan – Higher sensitivity than exercise ECG testing 1

High negative predictive value (99%) for 30 day ACS 2

Sensitivity diminishes after symptoms resolve – greatest sensitivity during symptoms

Results sometimes confounded by soft-tissue artefacts.

1 Early detection of myocardial ischaemia in the emergency department by rest or exercise (99m)Tc tracer myocardial SPET in patients with chest pain and non-diagnostic ECG. Epub 2001 2 The Erlanger chest pain evaluation protocol: a one-year experience with serial 12-lead ECG monitoring, two-hour delta serum marker measurements, and selective nuclear stress testing to identify and exclude acute coronary syndromes. Ann Emerg Med. 2002

CT Coronary Angiogram (CTCA) CTCA provides anatomic rather than functional

information Has a strong negative predictive value 99.3 in

excluding major adverse cardiac outcomes Good for excluding CHD if calcium burden is likely low Disadvantages

Radiation Risk Use of contrast (renal impairment) Functional effect of stenosis not assessedA meta-analysis of 64-section coronary CT angiography findings for predicting 30-day major adverse cardiac events in patients presenting with symptoms suggestive of acute coronary syndrome. Acad Radiol. 2011

Cardiovascular MRI Insufficient data to support its use at this stage Potentially offers the capability of being able to identify: regional wall

motion abnormalities, perfusion defects, MI, and CAD without ionizing radiation.

Rest / Stress cMRI Disadvantages

Costs Availability Claustrophobia

Needs further evaluation/studies Stress cardiac magnetic resonance imaging with observation unit care reduces cost for patients with emergent chest pain: a randomized trial. Ann Emerg Med. 2010

Summary

Detailed chest pain history Risk stratification Ensure timely follow-up Organise appropriate outpatient investigations