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Detection of myocardial ischemia by 31P magnetic resonance spectroscopy during handgrip exercise
1First Department of Internal Medicine, Shiga University of Medical Science, Otsu, Japan.
Insights
Phosphocreatine to ATP (PCr/ATP) ratio changes detected by 31P magnetic resonance spectroscopy (MRS) during handgrip exercise can identify myocardial ischemia. This method is sensitive for detecting ischemia in patients with coronary artery disease.
Area of Science:
- Cardiology
- Biophysics
- Medical Imaging
Background:
- Myocardial ischemia in coronary artery disease causes metabolic changes.
- Previous studies used 31P magnetic resonance spectroscopy (MRS) to assess these changes.
- Direct comparison of 31P MRS with exercise 201Tl myocardial scintigraphy was lacking.
Purpose of the Study:
- To investigate if 31P MRS with handgrip exercise can detect myocardial ischemia.
- To compare 31P MRS findings with exercise 201Tl myocardial scintigraphy results.
Main Methods:
- Twenty-seven patients with coronary artery disease and 11 controls underwent 31P MRS during handgrip exercise.
- Patients were categorized based on exercise 201Tl scintigraphy: reversible (RD[+]) or fixed (RD[-]) defects.
- Phosphocreatine to ATP (PCr/ATP) ratios were measured at rest and during exercise.
Main Results:
- Significant differences in resting PCr/ATP ratios were observed among control, RD(+), and RD(-) groups.
- The RD(+) group showed a significant decrease in PCr/ATP ratio during exercise (1.60 to 0.96).
- No significant change in PCr/ATP ratio during exercise was observed in the RD(-) or control groups.
Conclusions:
- Exercise-induced alterations in the PCr/ATP ratio were specific to patients with reversible thallium defects.
- 31P MRS combined with handgrip exercise is a sensitive tool for detecting myocardial ischemia.
- This technique offers a valuable method for assessing ischemia in patients with coronary artery disease.
Background:
The metabolic changes of myocardial ischemia in patients with coronary artery disease assessed by 31P magnetic resonance spectroscopy (MRS) have been reported previously. A significant decrease in the ratio of phosphocreatine (PCr) to ATP during handgrip exercise in a group of patients with severe coronary artery disease has been demonstrated. However, there are no reports at present that directly compare cardiac 31P MRS data with exercise 201Tl myocardial scintigraphy, now established as one of the most important clinical methods to assess myocardial ischemia. The purpose of this study was to investigate whether 31P MRS with handgrip exercise testing is able to detect myocardial ischemia, demonstrated by exercise 201Tl scintigraphy.
Methods And Results:
Twenty-seven patients with severe stenosis of the left anterior descending coronary artery (> or = 75%) and 11 normal control subjects composed the present study. Patients were divided into two groups on the basis of exercise 201Tl scintigraphy: a reversible 201Tl defect group (RD[+]) who demonstrated redistribution at the late image and a fixed 201Tl defect group (RD[-]). While lying supine within the magnet, subjects performed handgrip exercise at 30% of maximal force once in every two cardiac cycles. 31P MR spectra were collected before and during handgrip exercise. Data were corrected for the saturation factor. ANOVA revealed significant differences among the three groups with respect to the mean +/- SD PCr/ATP ratio at rest (control, 1.85 +/- 0.28 > RD(+), 1.60 +/- 0.19 > RD(-), 1.24 +/- 0.30; P < .05). The PCr/ATP ratio decreased significantly from 1.60 +/- 0.19 at rest to 0.96 +/- 0.28 during exercise (P < .001) in the RD(+) group (n = 15). However, in the RD(-) group (n = 12), the ratio did not change significantly during handgrip exercise (1.24 +/- 0.30 at rest versus 1.19 +/- 0.28 during exercise). Similarly, the ratio did not change in the control group (n = 11) (1.85 +/- 0.28 at rest versus 1.90 +/- 0.23 during exercise).
Conclusions:
Contrary to normal subjects or patients with fixed thallium defects, the PCr/ATP ratio was significantly altered by exercise in patients with reversible thallium defects. These results suggest that 31P MRS with handgrip exercise testing is a sensitive method for detecting myocardial ischemia.