Reproducibility of anterior chamber angle measurements with anterior segment optical coherence tomography.

PURPOSE: To study the reproducibility and variability of iridocorneal angle (ICA) measurements by using anterior segment optical coherence tomography (AS-OCT) by expert and nonexpert observers. METHODS: Twenty-three healthy volunteers (nonexperts with a basic knowledge of ophthalmology) acquired five consecutive AS-OCT images in the enhanced anterior segment single mode in the 180° to 0° meridian of the right eyes of their peers. Two experts and the 23 nonexperts analyzed the images. The ICA software tool was used to determine the angle opening distance (AOD) and the trabecular iris surface area (TISA) at 500 and 750 µm. A random intercept model was fitted to evaluate the variability of acquiring an image. For both the experts and the nonexperts, inter- and intraobserver variability of analyzing an AS-OCT image was determined with the coefficient of variation (CV). Reproducibility was qualified by using the intraclass correlation coefficient (ICC). RESULTS: There was no statistically significant difference in the variability of acquiring an image. The range of intraobserver variability in image analysis was from 9.4% to 12.5% in the experts and from 4.2% to 17.4% in the nonexperts. Interobserver variability was 10.7% in the experts and 10.2% in the nonexperts. The reproducibility was high, 0.875 and 0.942 in the experts and 0.906 in the nonexperts. CONCLUSIONS: The overall reproducibility of the ICA measurements with the AS-OCT is good in open angles. Inter- and intraobserver variability showed similar mean values of reproducibility between the experts and nonexperts. The wide range of intraobserver variation in the nonexperts suggests that this group should undergo extensive instruction before routinely analyzing AS-OCT images.

Combined Impella and intra-aortic balloon pump support to improve both ventricular unloading and coronary blood flow for myocardial recovery: an experimental study.

Some patients in need of hemodynamic support do not respond to intra-aortic balloon pump (IABP) therapy. Hemodynamic stability can then be obtained by a more potent cardiac assist device, like the Impella catheter pump. Whether additional IABP support additional to Impella support can provide more optimal hemodynamic myocardial conditions is examined in this study. Seven sheep were implemented with IABP and Impella. An acute myocardial infarction was induced. Hemodynamic performance was assessed during baseline, during Impella support and IABP support individually, and during the combined Impella plus IABP support. The Impella support provided a reduction of afterload with 30% and an increase of coronary artery flow with 47%. The IABP increased coronary artery flow (13%), carotid artery flow (16%), and aortic ascending blood pressure (6%); a similar (but stronger) effect was provided when using the IABP support additional to Impella support and, respectively, increases of 33, 21, and 19% were established. The oxygen demand-supply ratio decreased by 25% due to the extra use of the IABP. A combination of IABP and Impella provides the most optimal hemodynamic myocardial conditions compared to either stand-alone support.

New ultrasonic radiation reduces cerebral emboli during extracorporeal circulation.

OBJECTIVE: Cardiac surgery is associated with intraoperative cerebral emboli, which can result in postoperative neurological complications. A new ultrasonic transducer (EmBlocker) can be positioned on the ascending aorta and activation of the EmBlocker is expected to divert emboli to the descending aorta, thereby decreasing emboli in the cerebral arteries. In this preliminary animal study, safety and efficiency of this technology were examined. METHODS: In 14 pigs (+/-70 kg), a median sternotomy was performed and the EmBlocker was positioned on the aorta ascendens at the level of the bifurcation of the aorta and the innominate artery. In one animal temperature measurements were performed. During these measurements, the EmBlocker was activated for four periods of 120 s of high power (1.5 W/cm(2)) and for four periods of 600 s of low power (0.5 W/cm(2)). In the safety study (n=6), the EmBlocker was activated twice the expected clinical duration (eight periods of 120 s of high power and, subsequently, one period of 20 min of low power). Tissue samples (control and sonicated) were collected after 1 week for histopathological evaluation (aorta, trachea, esophagus, vagus nerves). In the efficiency study (n=7), extracorporeal circulation was installed. Emboli (air and solid (1200, size 500 microm-750 microm)) were introduced in the proximal ascending aorta and the EmBlocker was alternately activated with high power for solid emboli injections and low power for air emboli injections. Transcranial Doppler (TCD) was used to analyse middle cerebral artery blood flow for occurrence of embolic signals, which were manually counted offline. RESULTS: Histopathology revealed no difference between control and sonicated tissue. There is a rise in temperature during EmBlocker activation, but in all measured tissues it was within limits; less then 42 degrees C for 2 min in the aorta wall directly under the EmBlocker. Use of the EmBlocker significantly reduced emboli in the cerebral arteries in an animal model; air emboli with 65% (left) and 69% (right) and solid emboli with 49% (left) and 50% (right). CONCLUSIONS: The new ultrasound technology can safely be applied and is capable of reducing emboli in the cerebral arteries during extracorporeal circulation. Use of the EmBlocker in cardiac surgery bears the potential to lower the risk of postoperative neurological complications. Clinical feasibility studies are in progress.

The acute effect of intra-aortic balloon counterpulsation during extracorporeal life support: an experimental study.

Hemodynamically unstable patients supported by an extracorporeal life support (ECLS) circuit often receive additional support by intra-aortic balloon pump (IABP). However, it is not established whether support of the failing heart is improved by adjunctive IABP in both peripheral cannulation (PC) and central cannulation (CC) settings. Seven sheep were supported by an IABP and an ECLS system which were cannulated centrally as well as peripherally. In each cannulation configuration, hemodynamic and cardiac function indices were measured at baseline, ECLS, and ECLS plus IABP. The primary variables were mean coronary artery flow (Qcor), diastolic pressure time index (DPTI), left ventricular (LV) pressure-volume area (PVA), and tension time index (TTI). Additional IABP with ECLS support (CC/PC) decreased LV afterload (LV systolic peak pressure -4%, P<0.05/-8%, P<0.02), as well as TTI -2%/-10% and PVA -10%/-12% (P<0.03). Coronary perfusion was increased by additional IABP: CC, Qcor, +9%, and DPTI, +18% (P<0.02); PC, Qcor,+6%, and DPTI, +11% (P<0.05). IABP augmented the myocardial oxygen supply/demand ratios (CC/PC): Qcor/(PVA.heart rate) (+21%/+22%, P<0.02) and DPTI/TTI (+27%/+24%, P<0.03). In case of low arterial pressure (<50 mm Hg) and reduced ECLS flow, the overall hemodynamic profile improved only with central cannulation. We conclude that in both central and peripheral ECLS cannulation settings, adjunctive IABP improves the myocardial oxygen supply demand balance. In case of low cardiac output and insufficient extracorporeal flow with PC, adjunctive IABP may be contraindicated.

Synchronously counterpulsating extracorporeal life support enhances myocardial working conditions regardless of systemic perfusion pressure.

OBJECTIVE: A new pulsatile extracorporeal life support (pECLS) system has entered the market. We wanted to investigate what potential advantages pECLS may have over current non-pulsatile systems (NPS). Our research was focused on the pump's functional interaction with the left ventricle and the coronary circulation. METHODS: Extensive hemodynamic measurements were performed during asynchronous and synchronous pECLS in 10 calves. The two extremes regarding LV afterload, namely systolic arrival (SA) and diastolic arrival (DA) of the pump pulse were studied. RESULTS: SA was associated with increased oxygen consumption (+57%) and decreased diastolic coronary perfusion (-43%). DA increased left ventricular output (DA: 4.5+/-2.4 l/min vs SA: 3.5+/-2.2 l/min), LV ejection fraction (+10%), and ventricular efficiency (+17%). Mean aortic pressure and mean coronary flow were only marginally affected by pulse incidence. Systolic impairment was more pronounced with higher bypass flows. These results indicate that myocardial working conditions can be optimized by phasing pECLS ejection into cardiac diastole. CONCLUSION: We conclude that during pECLS, myocardial working conditions can be improved by avoidance of systolic impairment. Synchronously counterpulsating pECLS could be a more economic and versatile alternative to NPS or NPS combined with intra-aortic balloon pumping. The potential benefits of synchronously counterpulsating pECLS over the current alternatives remain to be investigated.