Collateral-flow measurements in humans by myocardial contrast echocardiography: validation of coronary pressure-derived collateral-flow assessment

Aims Myocardial blood flow (MBF) is the gold standard to assess myocardial blood supply and, as recently shown, can be obtained by myocardial contrast echocardiography (MCE). The aims of this human study are (i) to test whether measurements of collateral-derived MBF by MCE are feasible during elective angioplasty and (ii) to validate the concept of pressure-derived collateral-flow assessment. Methods and results Thirty patients with stable coronary artery disease underwent MCE of the collateral-receiving territory during and after angioplasty of 37 stenoses. MCE perfusion analysis was successful in 32 cases. MBF during and after angioplasty varied between 0.060-0.876 mL min−1 g−1 (0.304±0.196 mL min−1 g−1) and 0.676-1.773 mL min−1 g−1 (1.207±0.327 mL min−1 g−1), respectively. Collateral-perfusion index (CPI) is defined as the rate of MBF during and after angioplasty varied between 0.05 and 0.67 (0.26±0.15). During angioplasty, simultaneous measurements of mean aortic pressure, coronary wedge pressure, and central venous pressure determined the pressure-derived collateral-flow index (CFIp), which varied between 0.04 and 0.61 (0.23±0.14). Linear-regression analysis demonstrated an excellent agreement between CFIp and CPI (y=0.88x+0.01; r2=0.92; P<0.0001). Conclusion Collateral-derived MBF measurements by MCE during angioplasty are feasible and proved that the pressure-derived CFI exactly reflects collateral relative to normal myocardial perfusion in human

The relative myocardial blood volume differentiates between hypertensive heart disease and athlete's heart in humans

Aims The adaptation of the myocardial microcirculation in humans to pathologic and physiologic stress has not been examined in vivo so far. We sought to test whether the relative blood volume (rBV) measured by myocardial contrast echocardiography (MCE) can differentiate between left ventricular (LV) hypertrophy (LVH) in hypertensive heart disease and athlete's heart. Methods and results Four groups were investigated: hypertensive patients with LVH (n=15), semi-professional triathletes with LVH (n=15), professional football players (n=15), and sedentary control individuals without cardiovascular disease (n=15). MCE was performed at rest and during adenosine-induced hyperaemia. The rBV (mL mL−1), its exchange frequency (β, min−1), and myocardial blood flow (mL min−1 g−1) were derived from steady state and refill sequences of ultrasound contrast agent. Hypertensive patients had lower rBV (0.093±0.013 mL mL−1) than triathletes (0.141±0.012 mL mL−1, P<0.001), football players (0.129±0.014 mL mL−1, P<0.001), and sedentary individuals (0.126±0.018 mL mL−1, P<0.001). Conversely, the exchange frequency (β) was significantly higher in hypertensive patients (11.3±3.8 min−1) than in triathletes (7.4±1.8 min−1), football players (7.7±2.3 min−1), and sedentary individuals (9.0±2.5 min−1). An rBV below 0.114 mL mL−1 distinguished hypertensive patients and triathletes with a sensitivity of 93% and a specificity of 100%. Conclusion Pathologic and physiologic LVH were differentiated non-invasively and accurately by rBV, a measure of vascularisation assessed by MC

The quantification of absolute myocardial perfusion in humans by contrast echocardiography Algorithm and validation

ObjectivesWe sought to test whether myocardial blood flow (MBF) can be quantified by myocardial contrast echocardiography (MCE) using a volumetric model of ultrasound contrast agent (UCA) kinetics for the description of refill curves after ultrasound-induced microsphere destruction.BackgroundAbsolute myocardial perfusion or MBF (ml·min−1·g−1) is the gold standard to assess myocardial blood supply, and so far it could not be obtained by ultrasound.MethodsThe volumetric model yielded MBF= rBV·β/ρT, where ρTequals tissue density. The relative myocardial blood volume rBV and its exchange frequency βwere derived from UCA refill sequences. Healthy volunteers underwent MCE and positron emission tomography (PET) at rest (group I: n = 15; group II: n = 5) and during adenosine-induced hyperemia (group II). Fifteen patients with coronary artery disease underwent simultaneous MCE and intracoronary Doppler measurements before and during intracoronary adenosine injection.ResultsIn vitro experiments confirmed the volumetric model and the reliable determination of rBV and βfor physiologic flow velocities. In group I, 187 of 240 segments were analyzable by MCE, and a linear relation was found between MCE and PET perfusion data (y = 0.899x + 0.079; r2= 0.88). In group II, resting and hyperemic perfusion data showed good agreement between MCE and PET (y = 1.011x + 0.124; r2= 0.92). In patients, coronary stenosis varied between 0% to 89%, and myocardial perfusion reserve was in good agreement with coronary flow velocity reserve (y = 0.92x + 0.14; r2= 0.73).ConclusionsThe volumetric model of UCA kinetics allows the quantification of MBF in humans using MCE and provides the basis for the noninvasive and quantitative assessment of coronary artery disease

Quantitative stress echocardiography in coronary artery disease using contrast-based myocardial blood flow measurements: prospective comparison with coronary angiography

AIM: To test whether quantitative stress echocardiography using contrast-based myocardial blood flow (MBF, ml x min(-1) x g(-1)) measurements can detect coronary artery disease in humans. METHODS: 48 patients eligible for pharmacological stress testing by myocardial contrast echocardiography (MCE) and willing to undergo subsequent coronary angiography were prospectively enrolled in the study. Baseline and adenosine-induced (140 microg x kg(-1) x min(-1)) hyperaemic MBF was analysed according to a three-coronary-artery-territory model. Vascular territories were categorised into three groups with increasing stenosis severity defined as percentage diameter reduction by quantitative coronary angiography. RESULTS: Myocardial blood flow reserve (MBFR)-that is, the ratio of hyperaemic to baseline MBF, was obtained in 128 (89%) territories. Mean (SD) baseline MBF was 1.073 (0.395) ml x min(-1) x g(-1) and did not differ between territories supplied by coronary arteries with mild (or=75% stenosis) disease. Mean (SD) hyperaemic MBF and MBFR were 2.509 (1.078) ml x min(-1) x g(-1) and 2.54 (1.03), respectively, and decreased linearly (r2 = 0.21 and r2 = 0.39) with stenosis severity. ROC analysis revealed that a territorial MBFR or=50% stenosis with 89% sensitivity and 92% specificity. CONCLUSION: Quantitative stress testing based on MBF measurements derived from contrast echocardiography is a new method for the non-invasive and reliable assessment of coronary artery disease in humans

Myocardial blood volume and coronary resistance during and after coronary angioplasty

Animal experiments have shown that the coronary circulation is pressure distensible, i.e., myocardial blood volume (MBV) increases with perfusion pressure. In humans, however, corresponding measurements are lacking so far. We sought to quantify parameters reflecting coronary distensibility such as MBV and coronary resistance (CR) during and after coronary angioplasty. Thirty patients with stable coronary artery disease underwent simultaneous coronary perfusion pressure assessment and myocardial contrast echocardiography (MCE) of 37 coronary arteries and their territories during and after angioplasty. MCE yielded MBV and myocardial blood flow (MBF; in ml · min(-1) · g(-1)). Complete data sets were obtained in 32 coronary arteries and their territories from 26 patients. During angioplasty, perfusion pressure, i.e., coronary occlusive pressure, and MBV varied between 9 and 57 mmHg (26.9 ± 11.9 mmHg) and between 1.2 and 14.5 ml/100 g (6.7 ± 3.7 ml/100 g), respectively. After successful angioplasty, perfusion pressure and MBV increased significantly (P < 0.001 for both) and varied between 64 and 118 mmHg (93.5 ± 12.8 mmHg) and between 3.7 and 17.3 ml/100 g (9.8 ± 3.4 ml/100 g), respectively. Mean MBF increased from 31 ± 20 ml · min(-1) · g(-1) during coronary occlusion, reflecting collateral flow, to 121 ± 33 ml · min(-1) · g(-1) (P < 0.01), whereas mean CR, i.e., the ratio of perfusion pressure and MBF, decreased by 20% (P < 0.001). In conclusion, the human coronary circulation is pressure distensible. MCE allows for the quantification of CR and MBV in humans

Myocardial contrast echocardiography for the distinction of hypertrophic cardiomyopathy from athlete's heart and hypertensive heart disease

BACKGROUND: Myocardial contrast echocardiography (MCE) is able to measure in vivo relative blood volume (rBV, i.e., capillary density), and its exchange frequency b, the constituents of myo-cardial blood flow (MBF, ml min-1 g-1). This study aimed to assess, by MCE, whether left ventricular hypertrophy (LVH) in hypertrophic cardiomyopathy (HCM) can be differentiated from LVH in triathletes (athlete's heart, AH) or from hypertensive heart disease patients (HHD). METHODS: Sixty individuals, matched for age (33 +/- 10 years) and gender, and subdivided into four groups (n = 15) were examined: HCM, AH, HHD and a group of sedentary individuals without LVH (S). rBV (ml ml-1), b (min-1) and MBF, at rest and during adenosine-induced hyperaemia, were derived by MCE in mid septal, lateral and inferior regions. The ratio of MBF during hyperaemia and MBF at rest yielded myocardial blood flow reserve (MBFR). RESULTS: Septal wall rBV at rest was lower in HCM (0.084 +/- 0.023 ml ml-1) than in AH (0.151 +/- 0.024 ml ml-1, p <0.01) and in S (0.129 +/- 0.026 ml ml-1, p <0.01), but was similar to HHD (0.097 +/- 0.016 ml ml-1). Conversely, MBFR was lowest in HCM (1.67 +/- 0.93), followed by HHD (2.8 +/- 0.93, p <0.01), by S (3.36 +/- 1.03, p <0.001) and by AH (4.74 +/- 1.46, p <0.0001). At rest, rBV <0.11 ml ml-1 accurately distinguished between HCM and AH (sensitivity 99%, specificity 99%), similarly MBFR < or =1.8 helped to distinguish between HCM and HHD (sensitivity 100%, specificity 77%). CONCLUSIONS: rBV at rest, most accurately distinguishes between pathological LVH due to HCM and physiological, endurance-exercise induced LVH

A high-resolution record of the atmospheric CO2 concentration from 60-20 kyr BP from the Taylor Dome ice core, Antarctica

A high-resolution record of the atmospheric CO2 concentration from 60 to 20 thousand years before present (kyr BP) based on measurements on the ice core of Taylor Dome, Antarctica is presented. This record shows four distinct peaks of 20 parts per million by volume (ppmv) on a millennial time scale. Good correlation of the CO2 record with temperature reconstructions based on stable isotope measurements on the Vostok ice core (Antarctica) is found