Practical points for nuclear cardiology

Pharmacologic stress myocardial perfusion imaging: A practical approach

Patient selection and scheduling

To perform pharmacologic stress MPI testing safely and obtain meaningful results, we perform 3 different levels of review of patient characteristics and safety factors. The first level of selection of patients for pharmacologic stress imaging is performed by the referring physician. Laboratory test requisition forms allow for the specification of the mode of stress. Referring physicians have varying levels of ability to assess their patients’ functional capacity and ability to perform treadmill

Patient preparation

Upon scheduling the examination, patients receive a set of written instructions that outline the time requirements, anticipated sequence of events, and possible side effects of pharmacologic stress testing. These instructions are available by mail, fax, and E-mail and are posted on our laboratory Web site. Patients are instructed to fast after midnight or, for tests starting after noon, to fast for 4 hours before testing. Diabetic patients are told to test their blood sugar level at home, if

Performance of pharmacologic stress testing

After completion of resting imaging, patients go to the treadmill room and electrocardiographic (ECG) monitoring equipment is applied. The blood pressure cuff is placed on the arm without the intravenous catheter. Infusion pumps, loaded with premixed syringes containing adenosine or dobutamine, are connected via flexible tubing to the patient’s intravenous catheter, with the patient lying supine (adenosine or dobutamine) or standing on the treadmill if low-level exercise is anticipated

Interpretation of pharmacologic stress MPI studies

Clinical observations from pharmacologic stress testing differ from those from exercise stress testing. Symptoms associated with vasodilator stress, in particular, are often nonspecific; chest discomfort or dyspnea occurring with adenosine infusion, for example, may be related to medication effect, myocardial ischemia, or both. Whereas coronary vasorelaxation is mediated by stimulation of adenosine A_2A receptors, other side effects such as atrioventricular block and bronchospasm are mediated by

Reporting of pharmacologic stress MPI findings

As for exercise stress MPI, symptoms, hemodynamic response to stress, occurrence of arrhythmias, and ECG response to stress are reported for pharmacologic stress MPI. The final report clearly notes the type of pharmacologic stress used and whether adjunctive low-level exercise was performed. Interpretation of perfusion images is performed as for exercise stress MPI, with note made of the presence or absence of transient ischemic dilation, difference in calculated left ventricular ejection

Conclusion

In the substantial proportion of patients in whom exercise stress testing is not possible, pharmacologic stress MPI is an important tool in the detection of ischemic heart disease. With careful attention to patient selection, performance of the pharmacologic stress protocols, addition of adjunctive low-level exercise stress whenever possible, and measures to optimize image quality, important diagnostic and prognostic information can be obtained, comparable to that produced with standard

Acknowledgment

We acknowledge the efforts of the nursing, technical, and support staff of the Mission Internal Medical Group nuclear cardiology laboratory and their unwavering focus on quality.

The authors have indicated they have no financial conflicts of interest.