Kjærgaard, Jesper

BACKGROUND: Cardiac troponin (cTn) is key in diagnosing myocardial infarction (MI). After MI, the clinically observed half-life of cTn has been reported to be 7 to 20 hours, but this estimate reflects the combined elimination and simultaneous release of cTn from cardiomyocytes. More precise timing of myocardial injuries necessitates separation of these 2 components. We used a novel method for determination of isolated cTn elimination kinetics in humans. METHODS: Patients with MI were included within 24 hours after revascularization and underwent plasmapheresis to obtain plasma with a high cTn concentration. After at least 3 weeks, patients returned for an autologous plasma retransfusion followed by blood sampling for 8 hours. cTn was measured with 5 different high-sensitivity cTn assays. RESULTS: Of 25 included patients, 20 participants (mean age, 64.5 years; SD, 8.2 years; 4 women [20%]) received a retransfusion after a median of 5.8 weeks (interquartile range, 5.0–6.9 weeks) after MI. After retransfusion of a median of 620 mL (range, 180–679 mL) autologous plasma, the concentration of cTn in participants’ blood increased 4 to 445 times above the upper reference level of the 5 high-sensitivity cTn assays. The median elimination half-life ranged from 134.1 minutes (95% CI, 117.8–168.0) for the Elecsys high-sensitivity cTnT assay to 239.7 minutes (95% CI, 153.7–295.1) for the Vitros high-sensitivity cTnI assay. The median clearance of cTnI ranged from 40.3 mL/min (95% CI, 32.0–44.9) to 52.7 mL/min (95% CI, 42.2–57.8). The clearance of cTnT was 77.0 mL/min (95% CI, 45.2–95.0). CONCLUSIONS: This novel method showed that the elimination half-life of cTnI and cTnT was 5 to 16 hours shorter than previously reported. This indicates a considerably longer duration of cardiomyocyte cTn release after MI than previously thought. Improved knowledge of timing of myocardial injury may call for changes in the management of MI and other disorders with myocardial injury.

Background— Left ventricular diastolic dysfunction (DD) is common after myocardial infarction (MI) despite preservation of left ventricular ejection fraction, yet it remains unclear how or whether DD affects cardiac hemodynamics with stress. Methods and Results— Invasive hemodynamic exercise testing was performed in 46 patients with a recent MI and left ventricular ejection fraction >45% and in 10 healthy volunteers. MI patients were enrolled prospectively and divided into those with DD (MI+DD; left atrial volume index >34 mL/m 2 and diastolic E/e′ ratio>8; n=35) and those without DD (MI–DD; left atrial volume index <34 mL/m 2 and E/e′ ratio<8; n=11). All underwent a supine cycle ergometer test with simultaneous right heart catheterization and echocardiography. At rest, 10 patients in MI+DD (29%) had pulmonary capillary wedge pressure >15 (14±4 mm Hg), whereas none of the MI−DD (10±2 mm Hg) or controls (9±2 mm Hg) displayed pulmonary capillary wedge pressure elevation ( P =0.03). During exercise, an abnormal rise in pulmonary capillary wedge pressure (>25 mm Hg) was observed in 94% of MI+DD (36±6 mm Hg) compared with 36% of MI−DD (24±6 mm Hg) and none of the controls (16±6 mm Hg; P <0.0001). Exercise right atrial pressure was the highest in MI+DD followed by MI−DD and control (15±5 versus 9±4 versus 7±5 mm Hg; P <0.001), whereas no difference in cardiac index was found between groups. Conclusions— In post-MI patients with preserved ejection fraction and left ventricular DD, cardiac output with exercise is maintained at the expense of substantially increased filling pressure. DD and loss of diastolic reserve may promote progression from stage B to stage C heart failure after MI. (Circ Heart Fail. 2012;5:-451.)