A modified protocol for retrograde cerebral perfusion: magnetic resonance spectroscopy in pigs.

Objectives: Retrograde cerebral perfusion (RCP) has been employed to protect the brain during cardiovascular surgery, requiring temporary hypothermic circulatory arrest (HCA). However, the protocol used for RCP remains to be modified if prolonged HCA is expected. The aim of this study was to determine the efficacy of a modified protocol for this purpose.

Can stunned hearts be resuscitated? Evaluation of aspartate/glutamate secondary blood cardioplegia using magnetic resonance spectroscopy.

Objectives: Reperfusion of ischemic hearts with warm, substrate-enriched, blood cardioplegia may alleviate post-ischemic metabolic and functional derangements. This study investigates this possibility using (31)P magnetic resonance (MR) spectroscopy. Methods: Fifteen blood-perfused Langendorff pig hearts were subjected to 30 min of total, normothermic ischemia.

Adipose-derived stem cells are an effective cell candidate for treatment of heart failure: an MR imaging study of rat hearts.

This study assessed the potential therapeutic efficacy of adipose-derived stem cells (ASCs) on infarcted hearts. Myocardial infarction was induced in rat hearts by occlusion of the left anterior descending artery (LAD). One week after LAD occlusion, the rats were divided into three groups and subjected to transplantation of ASCs or transplantation of cell culture medium (CCM) or remained untreated.

Alternate antegrade/retrograde perfusion: an effective technique to preserve hypertrophied hearts during valvular surgery.

Objective: Continuous antegrade perfusion (AP) may interfere with surgical precision. Continuous retrograde perfusion (RP), on the other hand, cannot sustain the empty-beating hypertrophied hearts. Therefore, alternate antegrade/retrograde perfusion (A(A/R)P) may be a rational technique to preserve the hypertrophied hearts.

The effects of simultaneous antegrade/retrograde cardioplegia on cellular volumes and energy metabolism.

Background And Aim Of The Study: Simultaneous antegrade/retrograde cardioplegia (SARC) has been employed frequently during cardiac surgery to preserve the jeopardized myocardium. However, retrograde perfusion of SARC may interfere with myocardial drainage and disrupt myocardial fluid homeostasis, which may affect the myocardial energy metabolism and contractile function. The study was, therefore, designed to assess the effects of SARC on myocardial fluid homeostasis, cellular volumes, and energy metabolism.

Superparamagnetic iron oxide does not affect the viability and function of adipose-derived stem cells, and superparamagnetic iron oxide-enhanced magnetic resonance imaging identifies viable cells.

The objectives of this study were (1) to determine whether superparamagnetic iron oxide (SPIO) affects viability, transdifferentiation potential and cell-factor secretion of adipose-derived stem cells (ASCs); and (2) to determine whether SPIO-enhanced magnetic resonance (MR) imaging highlights living stem cells. Rat ASCs were incubated in SPIO-containing cell culture medium for 2 days. The SPIO-treated ASCs were then subjected to adipogenic, osteogenic and myogenic transdifferentiation.

Identification of chronic myocardial infarction with extracellular or intravascular contrast agents in magnetic resonance imaging.

Aim: To determine whether extracellular or intravascular contrast agents could detect chronic scarred myocardium in magnetic resonance imaging (MRI).

Methods: Eighteen pigs underwent a 4 week ligation of 1 or 2 diagonal coronary arteries to induce chronic myocardial infarction. The hearts were then removed and perfused in a Langendorff apparatus.

Surgery for cardiac valves and aortic root without cardioplegic arrest ("beating heart"): experience with a new method of myocardial perfusion.

Simultaneous antegrade/retrograde warm blood perfusion with a beating heart has not been previously reported as a mean of protecting hypertrophied hearts in cardiac valve and aortic root surgeries. Similarly, beating heart mitral valve surgery via the trans-septal approach with the aorta unclamped, is a novel technique. We, herein, report a series of 346 patients with a variety of cardiac pathologies who were operated upon utilizing a new modality of myocardial perfusion.

Unclamping the inferior vena cava during retrograde cerebral perfusion increases the safe range of retrograde perfusion pressures and improves brain perfusion.

We investigated the effect of different methods of management of the inferior vena cava (IVC) during retrograde cerebral perfusion (RCP) on the relationships between RCP pressure, regional cerebral blood flow, tissue oxygenation, and intracranial pressure (ICP). Fourteen pigs were subjected to hypothermic (15 degrees C) RCP at RCP pressures varying from 10 to 110 mmHg with clamping (closed group, n=7) or without clamping of the IVC (open group, n=7). Intracranial pressures increased more slowly in the open group than in the closed group and were significantly lower at any level of RCP pressure in the open group than in the closed group.

Does normothermic normokalemic simultaneous antegrade/retrograde perfusion improve myocardial oxygenation and energy metabolism for hypertrophied hearts?

Background: Beating-heart valve surgery appears to be a promising technique for protection of hypertrophied hearts. Normothermic normokalemic simultaneous antegrade/retrograde perfusion (NNSP) may improve myocardial perfusion. However, its effects on myocardial oxygenation and energy metabolism remain unclear.

Increased pressure during retrograde cerebral perfusion provides better preservation of the Na+, K+-ATPase activity.

This study was carried out to determine if increased perfusion pressure during retrograde cerebral perfusion (RCP) provides better preservation of the brain Na+, K+-ATPase activity. Twenty pigs were subjected to anesthesia alone (control group, n=5), hypothermic circulatory arrest (HCA) (HCA group, n = 5), HCA+RCP at perfusion pressures of 24-29 mmHg (Low-pressure group, n=5), or HCA+RCP at perfusion pressures of 34-40 mmHg (High-pressure group, n = 5). The brain was harvested for the measurement of tissue Na+, K+-ATPase activity.

Keeping the heart empty and beating improves preservation of hypertrophied hearts for valve surgery.

Objective: This study was designed to determine whether keeping the heart empty and beating improved myocardial fluid homeostasis and energy metabolism of hypertrophied pig hearts in comparison with cardioplegic arrest.

Methods: Twenty piglets underwent a 8-weeks (corrected) ascending aortic banding to induce left ventricular hypertrophy. Isolated hypertrophied hearts were divided into 4 groups (n = 5 in each group).

Tissue edema does not change gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA)-enhanced T1 relaxation times of viable myocardium.

Purpose: To determine whether tissue edema changes gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA)-enhanced T1 relaxation times of the viable myocardium.

Materials And Methods: A total of 16 isolated pig hearts were divided into four groups (N=4/group) and perfused in a Langendorff apparatus. Gd-DTPA was injected into the aortic perfusion line.

Use of a pH-stat strategy during retrograde cerebral perfusion improves cerebral perfusion and tissue oxygenation.

Background: Although it is well documented that the use of a pH-stat strategy during hypothermic cardiopulmonary bypass improves cerebral blood flow, an alpha-stat strategy has been almost exclusively used during retrograde cerebral perfusion. We investigated the effects of pH-stat and alpha-stat management on brain tissue blood flow and oxygenation during retrograde cerebral perfusion in a porcine model to determine if the use of a pH-stat strategy during retrograde cerebral perfusion improves brain tissue perfusion.

Methods: Fourteen pigs were managed by an alpha-stat strategy (alpha-stat group, n = 7) or by a pH-stat strategy (pH-stat group, n = 7) during 120 minutes of hypothermic retrograde cerebral perfusion.

Is maintenance of cerebral hypothermia the principal mechanism by which retrograde cerebral perfusion provides better brain protection than hypothermic circulatory arrest? A study in a porcine model.

Objective: Retrograde cerebral perfusion (RCP) provides better brain protection than hypothermic circulatory arrest (HCA) alone. The mechanism by which RCP improves brain protection during circulatory arrest remains unknown. The purpose of the study in pigs was to determine if RCP improves brain protection mainly as a result of its ability to maintain cerebral hypothermia.

Mapping myocardial viability using interleaved T1-T2* weighted imaging.

The present study was to evaluate the efficacy of our interleaved T1-T2* weighted imaging for assessing myocardial viability. The left anterior descending coronary artery (LAD) of pig hearts (n = 7) were occluded for 2 h, followed by 1 h reperfusion. After removed from animals, the hearts were perfused in a Langendorff apparatus with a mixture of pig blood and crystalloid solution in 1:1 ratio.

Retrograde cardioplegia.

Objective: This study was undertaken to compare the efficacy of retrograde cardioplegia for myocardial perfusion with that of antegrade cardioplegia at the same flow rate.

Methods: Colored microspheres were used in rat hearts to assess the capillary flow of cardioplegia solution. Myocardial perfusion was evaluated with magnetic resonance imaging in pig hearts.

Increased pressure during retrograde cerebral perfusion in an acute porcine model improves brain tissue perfusion without increase in tissue edema.

Background: There is a significant lack of scientific data to support the clinically accepted view that 25 to 30 mm Hg is the maximum safe perfusion pressure during retrograde cerebral perfusion (RCP). This study was designed to investigate whether perfusion pressure greater than 30 mm Hg during RCP is beneficial to the brain during prolonged HCA in an acute porcine model.

Methods: Sixteen pigs underwent 120 minutes of circulatory arrest in conjunction with RCP at a perfusion pressure of either 23 to 29 mm Hg (group L, n = 8) or 34 to 40 mm Hg (group H, n = 8) at 15 degrees C, followed by 60 minutes of normothermic cardiopulmonary bypass.

Simultaneously monitoring both T(1) and T(2)* signal intensities on a bolus injection of Gd-DTPA may distinguish infarcted myocardium.

Purpose: To determine whether injured myocardium may be identified by simultaneously monitoring contrast-induced T(1) and T(2)* signal intensity time-course changes with an interleaved T(1)-T(2)* imaging sequence.

Materials And Methods: Gadolinium-diethylene triamine pentaacetic acid (0.05 mmol/ kg) was injected as a bolus into ex vivo pig hearts, and simultaneous T(1) and T(2)* time-courses were obtained during the first pass.