ACS - Stress Testing

Therefore, based on current data, diagnostic stress testing is recommended for patients with a low to moderate pretest probability of CAD but is unlikely to be helpful in those at very low risk or high risk

ECG-Based Exercise Treadmill Testing The most commonly used definition of a positive exercise test result from an ECG standpoint is 1 mm of horizontal or downsloping ST-segment depression or elevation for at least 60 to 80 milliseconds after the end of the QRS complex.

Table 55-5 Contraindications to Exercise Testing

Absolute

 Acute myocardial infarction (within 2 d)
 High-risk unstable angina
 Uncontrolled cardiac dysrhythmias causing symptoms or hemodynamic compromise
 Symptomatic severe aortic stenosis
 Uncontrolled symptomatic heart failure
 Acute pulmonary embolus or pulmonary infarction
 Acute myocarditis or pericarditis
 Acute aortic dissection

Relative*

 Left main coronary stenosis
 Moderate stenotic valvular heart disease
 Electrolyte abnormalities
 Severe arterial hypertension (>200 mm Hg systolic, >110 mm Hg diastolic)
 Tachydysrhythmias or bradydysrhythmias
 Hypertrophic cardiomyopathy and other forms of outflow tract obstruction
 Mental or physical impairment leading to inability to exercise adequately
 High-degree atrioventricular block

Echocardiography . Advantages of stress echocardiography over exercise treadmill testing are its higher sensitivity and specificity for significant coronary disease and nondependence on the ECG.

Overall, stress echocardiography is associated with 80% sensitivity and 84% specificity when evaluating for significant coronary disease.55 Thus, it is superior to ECG-based stress testing. When evaluated among low-risk ED patients, three studies have reported NPVs for subsequent cardiac events to be 97% to 100%, comparable to that of stress testing using nuclear imaging techniques.54

Nuclear Medicine

Combined with conventional ECG-based stress testing, thallium imaging offers improved sensitivity and specificity for detection of significant CAD over ECG-based testing alone. Furthermore, thallium testing (or other perfusion imaging) is likely to be of value in patients who would not otherwise benefit from stress testing due to a confounding or potentially masking abnormal baseline ECG.

Sensitivities/Specificities

TREADMILL: sens spec

Overall 68% 77%

ED 90% 50%

SPECT

Overall 88% 77%

ED 86% 74%

ECHO

Overall 76% 88%

ED 47% 99%

which test to use?

ETT- no baseline ST segment abnormalities (no LBBB LVH w/strain), no digoxin use, Beta blockers and CCB ok...and if a negative result will just meant the person is going to get the next test...

Def of a positive treadmill:

1. >1mm horizontal or downsloping ST segment depression or elevation at 80ms after J point
2. significant arrythmias
3. decreased systolic BP of > 10 mmHg
4. significant symptoms

a negative stress test has @ 98% negative predictive value.

does a postive stress mandate admission? not necessarily (yes at Harbor), the following are predictive of L main disease or severe multi vessel disease:

1. ST depression > 2.5mm
2. serious ventricular arrythmias
3. ST depression within 3 minutes of beginning
4. prolonged >8 minute ST segment recovery
5. hypotension >10mmHb during test or diastolic HTN >110 during test.

these either need admission or at least a discussion with a cardiologist.

Utility of past tests

Angiography- if normal, progrssion to greater than 50% occlusion is unlikely within five years.

if <50% occlusion, about 30% progress to >50% obstruction at 3 years.

the change in chest pain and risk factors is predictive of progression (a diabetic with BS OOC not taking his/her lipid meds can accelerate much faster than your ordinary guy that does everything he should be doing...)

SPECT or EST-

<1% cardiac event rate at one year in patients with normal tests.

Bottom line:some low risk patients (10%) will have an adverse event within 31 months of initial evaluation, these are most likely the "higher risk" segment of the low risk population and therefore are quite likely to have some outpatient testing done within the next 31 months.

10 mets good 10 yr prognosis

85% max hr is adequate est

ECG Stress Testing

Protocol

1. need to reach 85- 100% maximum heart rate
2. max heart rate is 220- age
3. exercise capacity reported in minutes or met eq of ox consumption
4. test is adequate if >6 METs reported
5. test stopped when target heart rate reached
6. test also stopped if BP decrease more than 10mm, sustained v- tach, st elevation >1mm, chest pain, dizziness.
7. relative stop indications- st depression >2mm, arr, BP>250/115, claudication, SOB, BBB
8. Positive test if horizontal or downsloping st depression >1mm for 60 - 80ms, inappr slow heart rate, decrease in BP, sust V tach, st elevation
   1. if positive then need angio
   2. if equivocal- do stress echg or nuclear scan
   3. no beta blockers, ca channel blockers or nitrates

Source

6/06 MISTRY