Detection of myocardial infarction by dual-source coronary computed tomography angiography using quantitated myocardial scintigraphy as the reference standard.

BACKGROUND: Dual-source coronary computed tomography angiography (DS-CTA) has the potential to assess both coronary anatomy and myocardial perfusion. We studied the ability of DS-CTA to detect myocardial infarction (MI) compared to a reference standard of technetium Tc(99)m sestamibi single photon emission computed tomography (SPECT). METHODS: 122 patients with suspected or known coronary artery disease (age 60 (SD 11) years, 36% females) were evaluated by both DS-CTA and SPECT. SPECT-MI size was quantitated using a threshold value of 60% of peak counts on the resting images. MI on DS-CTA was defined as transmural or subendocardial hypoenhancement (<50% of surrounding myocardium), which persisted in both diastolic and systolic reconstructions and was concordant with a coronary artery territory. The performance of DS-CTA to detect SPECT-MI was determined in a blinded, vessel-based analysis. RESULTS: 366 vessel territories were analysed (122 patients x3). SPECT revealed 20 vessel territories with MI (involving 17 patients). 15/20 (75%) of these vessel territories were also detected by DS-CTA. An additional seven MIs were detected by DS CTA only (considered as false positive). Thus, the sensitivity of DS-CTA for detection of SPECT-MI was 75% (95% CI 56% to 94%), specificity 98% (97% to 100%), positive predictive value 68% (49% to 88%) and negative predictive value 99% (97% to 100%). DS-CTA detected 10/11 (91%) larger MIs (involving >5% of left ventricular (LV) mass by SPECT). For the 15 concordant MIs (in both SPECT and DS-CTA) the mean difference in MI size between modalities was 0.5% (4.6%) of LV mass (95% CI -8.6% to 9.5%). CONCLUSIONS: DS-CTA myocardial perfusion imaging showed moderate sensitivity and positive predictive value but high specificity and negative predictive value for detection of SPECT-MI. Most large infarcts (>5% of LV mass) were detected by DS-CTA. When MI was detected by both modalities, there was a good correlation between infarct sizes quantitated by DS-CTA vs SPECT.

Severe orthostatic hypotension following weight reduction surgery.

Surgical interventions for morbid obesity are common practice in many countries, especially when other treatment options have failed or when rapid weight loss is desired. The association between weight and blood pressure is well established, especially the paradigm of obesity-related hypertension. We describe a 45-year-old obese woman with a medical history of hypertension and type 2 diabetes mellitus who lost 57 kg within a few months after a weight reduction surgery. She suffered from severe orthostatic hypotension, which probably resulted from sympathetic nervous system dysfunction. Our patient's clinical status improved with pharmacological interventions, but her symptoms resolved completely after she gained weight following a surgical reversal of the gastric partitioning owing to a local complication. Autonomic nervous system activity does change with the changes in body weight, but after evaluation of this patient, we believe that rapid weight loss may impair sympathetic function and blood pressure control. Although losing weight is a known treatment option for hypertension, exaggerated reversal of obesity-related hypertension might result in orthostatic hypotension.