What is the most appropriate test to assess the coronary arteries in a 50-year-old male with recurrent chest tightness radiating to the shoulder, a family history of sudden death, and an electrocardiogram (ECG) showing left bundle branch block (LBBB)?

Pharmacologic Stress Myocardial Perfusion Imaging (Option A)

In this 50-year-old male with typical angina symptoms, significant family history of premature sudden death, and left bundle branch block on ECG, pharmacologic stress myocardial perfusion imaging with dipyridamole or adenosine is the most appropriate test to assess the coronary arteries.

Primary Recommendation Rationale

• Pharmacologic stress myocardial perfusion imaging (specifically with dipyridamole or adenosine) is the first-line diagnostic test for patients with LBBB, regardless of ability to exercise 1, 2
• Exercise ECG is contraindicated in LBBB because it produces false-positive septal perfusion defects with unacceptably low specificity (reported as 33%), yielding diagnostic accuracy of only 36-60% 1
• The altered pattern of cardiac activation in LBBB causes electrical and mechanical ventricular dyssynchrony that fundamentally impairs wall motion-based assessments 3

Why Other Options Are Inappropriate

Exercise ECG (Option C) - Contraindicated

• Exercise stress testing should never be used in patients with LBBB due to tachycardia-induced reversible septal defects even without left anterior descending artery disease 1
• The specificity drops to 33% with diagnostic accuracy of 36-60%, making results uninterpretable 1
• This patient has typical angina with high pretest probability—exercise ECG would provide misleading information 1

CT Angiography (Option B) - Not First-Line

• While CT angiography has sensitivity of 93-97% and specificity of 80-90% for detecting coronary disease, it is not the preferred initial diagnostic test in symptomatic patients with LBBB 1
• CT angiography provides only anatomical data without functional ischemia assessment, and identifying stenosis doesn't confirm it produces ischemia 1
• Guidelines recommend CT angiography only for intermediate pretest probability patients or those with indeterminate functional testing results 1
• This patient has high pretest probability given typical angina symptoms, family history of premature sudden death at age 46, and age 50—making functional testing more appropriate 1

Calcium Scoring CT (Option D) - Inadequate

• Coronary artery calcium scoring has only 40% specificity for detecting significant coronary stenosis in symptomatic patients 1
• It is explicitly not recommended as a diagnostic test in symptomatic patients 1
• Calcium scoring cannot assess functional significance of lesions or guide immediate management decisions 1

Technical Implementation Details

Preferred Pharmacologic Agents

• Dipyridamole or adenosine are the specific agents recommended (not dobutamine) because they produce coronary vasodilation without the mechanical stress that causes artifacts in LBBB 1, 2
• Regadenoson is an acceptable alternative with a more favorable side-effect profile 1
• Dobutamine stress should be avoided as it produces false-positive results similar to exercise, with tachycardia-induced septal abnormalities 1

Imaging Technique

• Single-photon emission computed tomography (SPECT) with images at rest and during pharmacologic stress 2
• Tracers: ²⁰¹Thallium or ⁹⁹ᵐTechnetium-labeled compounds (sestamibi or tetrofosmin) 2
• Pharmacologic vasodilation with adenosine/dipyridamole achieves sensitivity of 98%, specificity of 84%, and diagnostic accuracy of 88-92% in LBBB patients 1

Clinical Context Supporting This Choice

High-Risk Features Present

• Typical angina pattern: chest tightness radiating to shoulder, relieved with rest after 4 minutes suggests stable angina 1
• Strong family history: relative died suddenly at age 46, indicating premature coronary disease and possible genetic predisposition 1
• Age 50 with symptoms: places patient in high pretest probability category requiring definitive functional assessment 1

Prognostic Value

• Normal pharmacologic stress myocardial perfusion scan indicates low likelihood of significant coronary disease, making invasive angiography unnecessary 2
• Abnormal results with moderate to large ischemic defects have likelihood ratio of 8.35 for perioperative MI or death, providing critical risk stratification 1
• The test provides both diagnostic and prognostic information to guide management decisions 1

Critical Pitfalls to Avoid

• Never combine exercise with dipyridamole in LBBB patients—this negates the benefit of pharmacologic stress 1
• Avoid dobutamine stress echocardiography in LBBB as it produces false-positive septal wall motion abnormalities 1
• Do not use exercise-based testing of any kind (ECG or imaging) in the presence of complete LBBB 1
• Contraindications to dipyridamole/adenosine include significant heart block, severe bronchospasm, and critical carotid disease—screen for these before testing 1