Several previous studies reported severe cases of angina, but no appropriate tests to evaluate myocardial perfusion for patients with CPAF have been established. Scientists evaluated the hemodynamic characteristics of CPAF using thallium-201 (Tl-201) single photon emission computed tomography ( SPECT ).

Coronary artery fistula ( CAF ) is a rare coronary anomaly consisting of an abnormal communication between a coronary artery and a cardiac chamber or the great vessels. With the increasing use of multi-detector computed tomography ( MDCT ), the number of incidentally found CAF has also increased with incidence upto 0.9%. The most common type of CAF found by MDCT studies is coronary-to-pulmonary artery fistula (CPAF) with prevalence of 0.17-0.67%.

Tl-201 SPECT was performed in 17 patients with CPAF, but without evidence of coronary artery disease on coronary computed tomography angiography ( CCTA ) (age, 58.5 ± 13.3 years; 8 men). Quantitative analysis  of scintigraphic data was performed. Additionally, perfusion abnormalities were compared with CCTA findings. Medical records were obtained to define clinical data, diagnostic findings, symptoms, management, follow-up data, and major adverse cardiac events (MACE).

Six patients (35.2%) showed perfusion abnormalities on SPECT studies and could be classified as follows: 3 patients, non reversible ischemia (3/17, 17.6%); 1 patient, mild ischemia (1/17, 5.8%); and 2 patients, moderate ischemia (2/17, 11.7%). During the follow-up, ten patients (58.8%) improved under medical management and 5 patients (29.4%) underwent surgical ligation for CPAF with symptomatic improvement in 4 patients.

Of the seven patients performed follow-up myocardial perfusion  SPECT , and symptomatic improvement correlated well with scintigraphic perfusion improvement in 6 patients No MACE was observed. The clear guidelines for the treatment of CPAF have not yet been established. Therefore, an objective tool for measurement of hemodynamic instability in patients with CPAF is needed. A nuclear stress test may be useful in determining whether myocardial ischemia is associated with CPAF 

The study is an exploration study to evaluate myocardial perfusion SPECT findings and stress and rest scores in patients with CPAF . Perfusion abnormality was detected by SPECT in the absence of CAD in 35.2% of patients with CPAF (6 out of 17). Tl-201 myocardial perfusion SPECT might be useful for determining the hemodynamic status and for risk stratification in patients with CPAF.