Myocardial perfusion imaging in evaluation of undiagnosed acute chest pain

Myocardial perfusion imaging is a relatively new technique in the emergency department management of acute chest pain. With improved sensitivity and specificity compared to traditional methods of risk stratification, an abnormal scan rapidly identifies individuals with acute perfusion abnormalities and allows the appropriate utilization of limited resources. Conversely, a normal scan allows prompt hospital discharge and is associated with excellent outcomes both in the short and medium terms. Acute chest pain myocardial perfusion imaging has been demonstrated to alter patient management and disposition and its routine use results in decreased costs in the intermediate risk population.

Postoperative radial artery angiography for coronary artery bypass surgery

OBJECTIVE

To compare radial artery (RA) patency with internal mammary artery (IMA) patency for coronary artery bypass surgery in our early experience.

METHODS

Symptomatic as well as asymptomatic patients with > or =1 RA coronary graft underwent postoperative angiography. Each anastomosis was considered separately. A string sign referred to a diffusely narrowed conduit, which did not fill the grafted coronary artery, as well as all occluded conduits. The raw value of P was adjusted for the testing of multiple hypotheses (P'). The patency data for each conduit was divided into two parts. 'Cut-off' stenosis for a conduit was the lowest dividing coronary stenosis at which a difference in patency rate with P< or =0.05 occurred.

RESULTS

One-hundred-and-twenty-nine patients had 137 radial arteries and 157 angiograms. Only the most recent angiogram was analyzed for each patient at 13+/-0.7 months (n=129). Overall patency for arterial conduit 91% (n=404) was not different from venous conduit 91% (n=42) and patency for RA 90% (n=226) was not different from IMA 92% (n=178), (P'=0.999). Cut-off stenosis for RA was 70% and IMA was 40%. Patent arterial conduit had a mean coronary stenosis of 85% and non-patent conduit 64%, (P'<0.001). Right coronary territory patency was 82 vs. 94% for other territories (P'=0.022). No overall differences in patency were noted for patients with sequential anastomoses, symptoms or coronary disease at the anastomosis at the time of surgery. Reversible ischaemia was detected in the distribution of only two of 14 string signs in patients undergoing sestamibi exercise protocol following angiogram.

CONCLUSION

There were no differences in patency between radial artery and internal mammary artery at 13 months post-operative. Lower coronary stenosis and right coronary territory predicted lower patency. The clinical importance of a string sign remains to be determined.

Myocardial perfusion scintigraphy: effect on diagnostic and clinical management algorithms

Research has demonstrated that myocardial perfusion imaging increases the sensitivity and specificity of stress electrocardiography. However, the additional effect of the perfusion component of a stress study on clinical management algorithms remains poorly defined.

METHODS

We prospectively assessed the decision-making process in 518 patients, from 191 clinicians, undergoing stress myocardial perfusion imaging in our departments. Each clinician was asked, by telephone interview, to define the probability of reversible myocardial ischemia and their management plan (i.e., no antianginal treatment, medical therapy or an invasive intervention) in three stages: pretest, after the stress data was made available and after completion of the perfusion study.

RESULTS

The results of the stress data alone influenced the estimate of the probability of reversible ischemia in 149 of 518 patients, and management strategy in 50 of 518 patients. The data from the perfusion component in isolation changed probability of reversible disease in 219 of 518 patients and altered clinical management in 77 of 518 patients. Of 103 patients in whom an invasive procedure was planned after the stress data, the availability of the perfusion data led to deferral of catheterization in 48 cases (46.6%). Conversely, of the 415 patients triaged to a noninvasive plan after stress data, only 29 (7.0%) were changed to an invasive strategy. Of note, only 2.3% of women changed from a conservative strategy as a consequence of the perfusion data, compared to 9.1% of men.

CONCLUSION

The perfusion component of a stress study has a significant effect on both estimation of clinical probability and the definition of patient management strategy. Myocardial perfusion imaging reduced the number of catheterizations in patients initially triaged to an invasive management strategy. Conversely, the effect of stress and perfusion data in patients triaged to conservative management on clinical grounds, especially women, remains less well defined.

Demonstration of viable, stunned myocardium with technetium-99m-sestamibi

Delayed improvement of left ventricular contractile function in the setting of acute ischemia followed by reperfusion ("stunned myocardium") has been observed in a number of clinical scenarios, and may have important clinical implications. At present, there are no widely accepted techniques available to demonstrate its presence. We report a case in which a rest 99mTc-sestamibi scan performed 12 hr after thrombolytic therapy in the setting of acute myocardial infarction demonstrated viable myocardium in a region that was akinetic by contrast ventriculography. After surgical revascularization, follow-up 99mTc-sestamibi images showed normal perfusion and radionuclide ventriculography demonstrated normal left ventricular function. Demonstration of preserved 99mTc-sestamibi myocardial uptake in the infarct zone despite an extensive region of akinesis by contrast ventriculography predicted the recovery of left ventricular function after revascularization in this case. This suggests that perfusion imaging with 99mTc-sestamibi early after myocardial reperfusion can detect stunned myocardium and thus facilitate the decision-making process regarding management of such patients.

Identification of penile prosthetic infection on 67gallium scan

We report on a patient who presented with unexplained fever 7 weeks after placement of a penile prosthesis. A whole body 67gallium scan demonstrated a peri-prosthetic infection, which was confirmed at surgery.

Cholecystokinin (CCK)-HIDA scintigraphy in patients with suspected gall-bladder dysfunction

Cholecystokinin hepatobiliary (CCK-HIDA) scintigraphy is used to triage patients with chronic abdominal pain and suspected gall-bladder dysfunction. This study evaluates the predictive value of CCK-HIDA for clinical outcome after surgical and medical therapy. Fifty-six patients (45 females), mean age 43 +/- 9 years, with otherwise normal investigations, including normal ultrasound, fasted for more than 8h and then had 70MBq technetium-99m-EHIDA injected. One and a half hours later 15 ng/kg CCK was infused over 45 min. Seventy minutes dynamic imaging commenced 5 min prior to infusion. An abnormal gall-bladder ejection fraction (GBEF) was defined as < 50%. Patients were treated medically, or by cholecystectomy, depending on the surgeon's overall assessment, including results of the CCK-HIDA study. Patient status was then obtained in 51/56 patients at least 3 months after the scan or at least 1 month after surgery. All surgical specimens were reviewed independently for pathological changes of chronic acalculous cholecystitis. Of the 11 patients with an abnormal gall-bladder ejection fraction, nine (82%) underwent cholecystectomy, all of whom achieved total symptomatic cure, while two patients underwent other therapy, both of whom remained symptomatically unchanged. Of the 40 patients whose gall-bladder ejection fraction was normal, only five (12.5%) underwent cholecystectomy, of whom four were cured and one partially improved at follow up. Of the 35 patients with a normal gall-bladder ejection fraction and who underwent forms of therapy other than cholecystectomy, nine were cured symptomatically, 13 improved, 10 remained unchanged and three were symptomatically worse at follow up.(ABSTRACT TRUNCATED AT 250 WORDS)