Good morning, everyone. My name is Dr. Krishna Patel. I'm a multimodality imager at Mount Sinai Hospital in New York City. And today I'm going to discuss a case which illustrates the role of PET in multimodality evaluation of coronary artery disease. I have no disclosures relevant to this talk. So this is a case of a 73-year-old female who initially presented with palpitations and exertional chest pain that has been going on for about three months, on and off, to the clinic. She has a past medical history of diabetes, hypertension, hyperlipidemia. Hypertension has been poorly controlled in this patient. She's also kind of borderline obese and has fatty liver. She presented with symptoms of palpitations that have been going on for about two weeks. And this exertional mid-sternal chest pain, which does not radiate anywhere, but comes on with exertion and is relieved with rest. And this has been going on off and on for about three months. She says that she's in great shape and she walks about 12 blocks on a daily basis. This is a typical New Yorker for you. And because of this, she was initially referred for a treadmill stress echo. She underwent a BOOST protocol where she did seven meds, did not have any ECG changes with stress and no symptoms with stress. She reached 105% of her target heart rate, did not really have a hypertensive response and abnormal hemodynamic response. These are post-stress images, as you can see here. There was kind of no wall motion abnormalities, and they also did not detect any evidence of increased diastolic pressures post-exercise. After this, she was basically medically treated, medically managed, but she was still having this occasional chest pain off and on. So after about a month, she was referred for coronary CT angiogram due to persistent exertional chest pain, and now she also had a new complaint of dyspnea and exertion. So you can see the LAD here, there are coronary calcification, which is what you would expect in a 73-year-old woman. Approximately mid-LAD, there seems to be a moderate disease. There is some blooming artifact, but mid-LAD seems to be about kind of intermediate moderate disease, and then there is some disease approximately as well, you can see here, which also kind of goes in the moderate-moderate to severe range. The FFR-CT in the LAD, in mid-to-distal LAD, was abnormal at 0.71. The circumflex for this patient, again, had some calcified disease. This was kind of questionable, but again, we ended up calling it a moderate disease. This patient also had motion, which made the CT slightly challenging. This is the distal circumflex, again, some calcifications. This is a slab artifact from motion, which makes the distal circumflex assessment difficult, but all in all, it looks like kind of moderate to severe disease in the mid-LAD, kind of proximal to mid-LAD, and then mid-circumflex as well. The distal circumflex was also abnormal on the FFR-CT, but because we thought that this was a slab artifact, we thought that that was probably artifactual from this. And the RCA had just diffuse, kind of non-obstructive disease, minor calcification. Overall, the colon calcium score for this patient was 799, significant. We read it as moderate stenosis, 50 to 69% in mid-LAD, mid-circumflex, distal circumflex, and non-obstructive CD, the RCA. And based on FFR-CT analysis, there may be a hemodynamically significant stenosis in the mid-to-distal LAD, and possibly the circumflex, which was found to be less likely. Because of this, the patient then was referred for a coronary angiogram. You can see that RCA just has just mild diffuse disease, nothing significant. The LAD here at the bifurcation and at the kind of diagonal has kind of intermediate stenosis, moderate. The OM and the circumflex also have moderate disease. This patient had IFR assessment of the LAD lesion as well as the OM and circ lesion, and the IFR was all non-obstructive, more than 0.8. Based on this, the patient continued to be medically managed, but after about two months, she continued to have occasional chest pain, which was also exertional in nature. It had improved, but it was still there. And because of this, she was then referred for a rest-stress rubidium PET. You can see that these are the perfusion images for this patient. Again, stress is on top, rest is on bottom. This is done with rubidium. We do not see any relative perfusion abnormalities, any reversible or fixed perfusion abnormalities. These are the gated PET images, normal EF at rest and stress. EF goes from 60% to 70%. We do not see any one motion abnormalities. And then when we look at the quantitative flow assessment in this patient, the rest flows are within kind of normal limit at one, and they're similar in all three coronaries, which is what you would expect in somebody with normal perfusion. When you look at stress flows, the stress flows are kind of moderately reduced in all coronary territories. You can see here that the stress flow in the LAD is 1.6, circumflex is 1.5, and RCA is 1.8. So they're kind of moderately reduced in all three coronary territories, and so is the floor reserve. The floor reserve was also reduced in all three coronary territories, and the global floor reserve is 1.6. Now, knowing that this patient does not have any significant epicardial obstructive CAD as evaluated using IFR on cath, this reduction in stress flow, as well as the floor reserve, was suggestive of presence of coronary microvascular dysfunction in this patient, and that being the etiology of her symptoms. This is how we read the PET. Given the floor reserve, the abnormal stress flow in the floor reserve is what made the study high risk and helped us diagnose coronary microvascular dysfunction in this patient where we'd already ruled out significant obstructive epicardial CAD. So the teaching points for this case is, again, when a negative treadmill stress does not rule out coronary microvascular disease, such as this patient, the sensitivity of an abnormal exercise treadmill study to identify microvascular disease is quite low. It's about 35%. FFR and IFR, as we know, is used to assess, looks at a pressure drop, FFR looks at a pressure drop, and it helps us assess epicardial CAD stenosis severity. Also worth noting, in this patient, particularly because she had motion, as well as coronary artery calcification, FFR CT may be less accurate in patients who have motion artifact or significant coronary artery calcification. It may result in false positives, such as this patient had. And PET, myocardial flow assessment, and PET myocardial flow reserve, also referred to as coronary flow reserve by a lot of people, can help us assess the hemodynamic severity of a disease across the entire coronary circulation, including the myocardial circulation, and as such, can help in diagnosing coronary microvascular disease in conjunction, when used in conjunction with an anatomic assessment. It's also important to note that CMD typically coexists with some epicardial atherosclerosis. It may be obstructive or non-obstructive atherosclerosis. It's present in more than 80% of patients with CMD. And then when we find this pattern, and we saw in this patient, reduction in PET myocardial flow reserve globally, without significant epicardial, obstructive epicardial coronary artery disease, that helps us diagnose coronary microvascular dysfunction and or diffuse atherosclerosis. Thank you. And you can email me with any questions.

PET

coronary artery disease

microvascular dysfunction

coronary circulation

hemodynamics