Fixed inferior defect, LBBB, asthma and a coffee three hours ago

The study cannot proceed as scheduled today.

• Caffeine. Caffeine is a competitive adenosine-receptor antagonist. For adenosine and regadenoson, caffeine (and theophylline) must be withheld for about 12 h; for dipyridamole, 24 h. Two cups 3 hours ago would blunt the hyperemic response and could produce a false-negative study. Reschedule, ideally the next morning after an overnight hold.
• Asthma. Adenosine and regadenoson can cause bronchospasm. Regadenoson is generally acceptable in mild-to-moderate, well-controlled asthma with a rescue inhaler immediately available and monitoring for wheeze; it should be avoided in severe or poorly controlled disease. She is on combination therapy but not on oral steroids, so she falls in the cautious-but-usable category - premedicate per protocol and have albuterol at hand.
• LBBB. Exercise produces a rate-dependent septal perfusion defect in LBBB that mimics LAD disease. A vasodilator is therefore preferred, and dobutamine - which raises heart rate - reproduces the artifact, making it a second choice rather than a first.
• Exercise is not feasible anyway because of her knees.

Plan: reschedule at least 12 h after caffeine, use regadenoson with asthma precautions and full reversal with aminophylline available, and document the caffeine history explicitly.

Start with the physics of the defect. In a patient with BMI 38, a persistent inferior defect with normal wall motion and a normal ejection fraction is the classic signature of diaphragmatic attenuation - the diaphragm lies between the inferior wall and the detector, and the effect is worse supine and worse with a large abdomen.

Steps that raise or lower your confidence:

1. Check the raw data for patient motion. Motion is a common cause of a 'fixed' defect that is not real.
2. Prone or upright imaging, or CT attenuation correction. If the inferior defect resolves when prone or with AC, attenuation was the explanation.
3. Gated images. Normal thickening and motion in the same territory argues against transmural scar, although nontransmural scar can still show preserved function.
4. Territory. An isolated inferior defect without any other abnormality, in a patient with atypical symptoms and a low-intermediate pretest probability, is more likely artifact than a solitary RCA infarct.

Next step: if the question still matters, move to a modality that solves the attenuation problem - Rb-82 PET with CT attenuation correction gives higher specificity, and a coronary calcium score or CCTA adds anatomic information. If her pretest probability were high or symptoms changed, angiography would be appropriate regardless of the perfusion result.

Explain the LBBB artifact in plain terms. LBBB alters septal activation and relaxation, and at higher heart rates it produces a perfusion defect in the septum - the territory of the LAD - that is not caused by a narrowed artery. It is usually mild to moderate, usually partly reversible, and it is much more pronounced with exercise than with vasodilator stress. That is exactly why her exercise study was the least suitable stress for her.

What this means for her:

• A septal defect in her next study should be interpreted cautiously; a defect in another territory, or one accompanied by a wall motion abnormality, carries much more weight.
• Her current inferior defect does not fit the LBBB pattern at all, which is why attenuation is the leading explanation, not LBBB.
• Her atypical symptoms and lack of troponin elevation put her at low-intermediate risk, so a normal or near-normal study would be genuinely reassuring and would support guideline-directed risk-factor management rather than immediate angiography.

Frame the uncertainty honestly: no test is 'wrong' - the prior study was performed under conditions that maximized artifact. The right response is to repeat it properly, not to distrust functional imaging altogether, and to let the result change management only if the finding is reproducible and territory-consistent.