Management of Atrial Fibrillation with Diminished Myocardial Flow Reserve and Preserved LVEF
This patient requires invasive coronary angiography with functional assessment (FFR/iFR) to evaluate for obstructive coronary artery disease, combined with aggressive medical therapy for atrial fibrillation rate control and anticoagulation, given the markedly diminished myocardial flow reserve indicating significant coronary microvascular dysfunction despite preserved LVEF. 1
Immediate Coronary Evaluation
The markedly diminished myocardial flow reserve across all three vascular territories, particularly the left circumflex, indicates either diffuse epicardial atherosclerosis or severe coronary microvascular dysfunction that warrants invasive assessment. 1, 2
In patients with heart failure or suspected chronic coronary syndrome with LVEF >35%, invasive coronary angiography with FFR, iFR, or QFR is recommended when there is very high pre-test likelihood of obstructive CAD or when functional imaging reveals concerning findings. 1
The PET findings of diminished myocardial flow reserve (MFR) in all territories suggest either balanced three-vessel disease (which can appear as "normal" relative perfusion) or diffuse coronary microvascular dysfunction. 2, 3
A coronary flow reserve <2 is independently associated with diastolic dysfunction and future major adverse cardiac events, especially heart failure with preserved ejection fraction events, making this finding prognostically significant. 1, 4
Atrial Fibrillation Management
Beta-blockers are the first-line medication for rate control in this patient, targeting a resting heart rate <110 bpm, as they effectively control ventricular response and are well-tolerated in patients with preserved ejection fraction. 5, 6
Metoprolol or atenolol should be initiated for rate control, as these agents are effective in reducing heart rate and improving symptoms in patients with preserved left ventricular function. 5, 6
The target should be lenient rate control with resting heart rate <110 bpm initially, which is non-inferior to strict control (<80 bpm) for mortality, stroke, and heart failure outcomes. 6
Avoid calcium channel blockers (diltiazem, verapamil) if there is any concern for reduced ejection fraction or decompensated heart failure, though they can be used if LVEF remains >40% and beta-blockers are contraindicated. 6, 7
Anticoagulation Strategy
Calculate the CHA₂DS₂-VASc score immediately and initiate direct oral anticoagulants (DOACs) for scores ≥2, as this significantly reduces stroke risk with lower bleeding rates compared to warfarin. 5, 7
Apixaban, rivaroxaban, or edoxaban are preferred over warfarin due to lower bleeding risk, particularly lower intracranial hemorrhage rates. 5, 7
Anticoagulation should be continued indefinitely based on CHA₂DS₂-VASc score, regardless of whether the patient remains in sinus rhythm, as silent atrial fibrillation recurrences can still cause thromboembolic events. 6, 7
Aspirin alone or aspirin plus clopidogrel are not recommended for stroke prevention in atrial fibrillation, as they provide inferior efficacy compared to anticoagulation. 5
Coronary Microvascular Dysfunction Management
In patients with heart failure with preserved ejection fraction and persistent symptoms with normal or non-obstructive epicardial coronary arteries, PET perfusion should be considered to detect or rule out coronary microvascular dysfunction. 1
The finding of reduced myocardial flow reserve with normal relative perfusion suggests either diffuse atherosclerosis or primary coronary microvascular dysfunction, both of which are associated with worse outcomes. 1, 4, 3
Coronary microvascular dysfunction was observed in up to 75% of patients with HFpEF and was associated with worse diastolic relaxation velocities, higher filling pressures, and increased risk of adverse events. 1
If invasive angiography reveals non-obstructive CAD, consider invasive coronary functional testing (coronary flow reserve measurement) to definitively diagnose microvascular dysfunction. 1
Medical Therapy Optimization
An ACE inhibitor or ARB, beta-blocker, and SGLT2 inhibitor (dapagliflozin or empagliflozin) are recommended to reduce the risk of heart failure hospitalization and improve outcomes. 1
Beta-blockers should be continued throughout treatment as they provide dual benefit for both atrial fibrillation rate control and heart failure prevention. 1, 5
SGLT2 inhibitors (dapagliflozin or empagliflozin) are recommended for patients with chronic coronary syndrome and heart failure to reduce the risk of hospitalization and death. 1
Optimize anti-ischemic and preventive therapies with the goal to reduce angina burden and improve clinical outcomes, including statin therapy for atherosclerotic disease. 1
Critical Pitfalls to Avoid
Do not dismiss the markedly diminished myocardial flow reserve as clinically insignificant simply because relative perfusion appears balanced—this pattern can indicate severe three-vessel disease or diffuse microvascular dysfunction. 2, 3
Global reductions in myocardial blood flow as a consequence of three-vessel CAD can result in "balanced" reduction that appears normal on relative perfusion imaging but is detected by absolute flow quantification. 3
Avoid using AV nodal blockers if there is any history or ECG evidence of pre-excitation (Wolff-Parkinson-White syndrome), as this can precipitate ventricular fibrillation. 6
Do not withhold anticoagulation based on bleeding risk scores alone—instead, optimize modifiable bleeding risk factors (hypertension control, avoidance of NSAIDs, correction of anemia). 7
Risk Stratification and Prognosis
The combination of diminished myocardial flow reserve, atrial fibrillation, and preserved LVEF places this patient at intermediate-to-high risk for future major adverse cardiac events. 1
Reduced coronary flow reserve (<2) is independently associated with diastolic dysfunction and increased risk of adverse events, especially heart failure with preserved ejection fraction events. 1, 4
The percentage of fixed myocardium on SPECT, transient ischemic dilation with stress, and reduced coronary flow reserve are all features associated with higher risk of major adverse cardiovascular events. 1
Patients with atrial fibrillation and coronary artery disease have higher mortality rates, making aggressive risk factor modification and medical therapy essential. 1