Stress Testing

Stress Testing¶

Update on Stress Testing[^1]

Exercise Treadmill Test¶

[Pooled data][1]
- Men: Sensitivity of 68% and Specificity of 77% for CAD
- Women: Sensitivity of 61% and Specificity of 70% for CAD
Not interpretable for ischemia if:
- Old LBBB
- Unable to reach target HR
- Baseline ST elevation
- Digoxin use
Duke Treadmill Score = Exercise Time - 5x Maximal ST depressions - 4 x Angina Index
- ≥5 is low risk
- 4 to -10 is intermediate risk
- ≤-11 is high risk
Absolute Contraindication to EXERCISE Stress Testing (Use Drugs + Imaging)
- Inability to exercise adequately due to physical or mental impairment (85% of predicted HR unable to be reached)
Note:
- ST depression <0.5 give 0 for DTS
- Resting ST-segment depression <1mm increases test sensitivity but decreases specificity with no change in overall accuracy
- Role less clear in RBBB
Exercise Capacity is the highest prognostic impact marker during exercise testing including MPI variables irrespective of CAD severity, Gender, Age

Stress Testing with Imaging¶

Includes:
- Exercise Nuclear Stress
- Pharmacologic Nuclear Stress
- Dobutamine Stress Echo
Indications for Stress Testing with Imaging (MPI/Nuclear/SPECT, CMR, or Echo)
- Indications:
  - Unable to exercise
  - Baseline EKG abnormalities limiting interpretation
    - LBBB, RBBB
  - Indeterminate findings on Exercise Stress Test
SPECT (99mTc-Sestamibi/Tetrofosmin)
- Thallium no longer used
- SPECT MPI

Pharmacologic Stress Testing¶

Requires Imaging
Indications
- Unable/unwilling to exercise
- Contraindication to exercise
  - AAA
  - Severe AS
  - HOCM
- LBBB/Pacemaker
- Interfering Medications
- ACS
Modes
- Vasodilator (3.5-4x increase in myocardial blood flow)
  - Kinetics
    - Decrease SBP/DBP, increase HR
  - Medications
    - Dipyridamole
      - SE (50%)
    - Adenosine
      - 10 second half-life
      - 4 minute and 6 minute protocols
      - IV aminophylline reversal possible
      - SE (80%): CP (57%), Dyspnea (15%), Flushing (25%), Headache (35%), 2^nd degree AV block in 4%
    - Regadenoson (Lexiscan)
      - EXERRT Trial: safe to combinding low-level exercise for better heart-to-gut/liver ratios
      - IV aminophylline reversal possible
      - SE (86%): Dyspnea (61%), Flushing (39%), Headache (35%), Dizziness (27%), CP (12%)
  - Absolute Contraindications
    - High-grade AV block or SSS <40
    - Active or severe bronchospasm (asthma, active wheezing)
    - Hypotension (stimulate A2A receptors on vascular smooth muscles, magnified from rest)/Hypertension >200/110
    - Caffeine within 12 hours
    - Theophylline within 48 hours
  - Relative Contraindications
    - Seizure disorder
    - Severe AS
    - Mobitz 1 2^nd-degree AV block
  - Discontinue for:
    - Bronchospasm
    - SBP <80 mmHg
    - Persistent/symptomatic 2^nd/3^rd degree AV block
    - CP and ST depression >2mm
- Dobutamine
  - Kinetics: Increase SBP and HR, Decrease DBP
  - USE: CI to Exercise and Vasodilator Stress Testing
  - SE(75%): Ischemic ST-depression (33%), CP (31%), Palpitations (29%), Significant SVT/VT (8-10%)

Positive Findings¶

≥ 1mm of horizontal or downsloping ST-segment depression or elevation 8 ms after the J-point during exercise or recovery
≥1mm ST-elevation in a lead without a baseline Q-wave
≥1mm AVR elevation
Ventricular Tachycardia
more than 1.5-2mm of upsloping ST-segment depression 8 ms after the J-point during exercise or recovery

Findings associated with poor outcomes¶

Poor exercise capacity (<5 METs)
- Patients achieving ≥10 METs have a 0.1%/year rate of cardiac death and 0.7%/year rate of nonfatal MI
Exercise-induced angina during minimal expenditure
Inability to achieve 85% age-predicted maximum HR with exercise
- Calculated as (220 - Age)
Fall in SBP below baseline during exercise
ST elevation
≥ 2mm ST-depression during minimal expenditure
- Maximum ST-segment deviation is a strong predictor of both cardiac death and composite cardiac death and nonfatal MI
Early onset or prolonged duration of ST depression during testing
- Rapid recovery is associated with a low rate of positive imaging or findings of CAD on angiography
ST depression in multiple leads
Ventricular couplets or tachycardia during minimal expenditure or recovery