Biomedical subjects

Ganghong Tian

Publications and source records attributed to Ganghong Tian.

5 recordsLinked to original sources

PubMed2006

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). Two groups underwent normothermic normokalemic simultaneous perfusion. The other 2 groups were subjected to normothermic hyperkalemic simultaneous perfusion and used as controls. Intramyocardial hydrostatic pressure was monitored with a microtip pressure transducer. Volumes of intracellular and extracellular compartments and myocardial energy metabolism were monitored by using phosphorus 31 magnetic resonance spectroscopy. RESULTS: Normothermic normokalemic simultaneous perfusion (NNSP) maintained intramyocardial hydrostatic pressure at a significantly lower level (13.0 +/- 0.6 mm Hg) compared with normothermic hyperkalemic simultaneous perfusion (NHSP) (23.3 +/- 1.2 mm Hg) during a 90-minute preservation. NNSP maintained the normal volume of the intracellular compartment throughout the preservation period, whereas NHSP caused significant enlargement (to 123% +/- 6% of its normal volume) of the intracellular compartment. Expansion of the extracellular compartment during preservation was significantly less in the NNSP group (124% +/- 6%) than in the NHSP group (152% +/- 7%). NNSP maintained normal levels of phosphocreatine and adenosine triphosphate until coronary perfusion flow was reduced to 50% of the initial control level. No decrease in energy metabolites was observed in the NHSP group even when coronary perfusion flow was reduced to 10% of the initial control level. CONCLUSIONS: Keeping the heart empty and beating improves myocardial fluid homeostasis for hypertrophied hearts relative to cardioplegic arrest. Its ability to maintain energy metabolism depends on the degree of coronary stenosis. This technique may be a promising protective strategy for hypertrophied hearts.

Animals↗

PubMed2005

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. Tissue edema was then induced by two hours of simultaneous arterial/venous perfusion (SAVP). Myocardial water content and T1 relaxation times were monitored throughout SAVP. The volumes of the extracellular and intracellular compartments were assessed using 31P MRS-detectable markers, phenylphosphonic acid (PPA) and dimethyl methylphosphonate (DMMP). RESULTS: Tissue water content in both viable and infarcted myocardium increased significantly during two-hour SAVP. However, Gd-DTPA-enhanced T1 relaxation times of the viable myocardium remained relatively unchanged. Infarcted myocardium, on the other hand, exhibited significant T1 shortening during SAVP. Furthermore, SAVP resulted in significant expansions of both extracellular and intracellular compartments, but the ratio of the volumes of the two compartments remained relatively constant. CONCLUSION: Tissue edema in the viable myocardium does not increase the relative distribution volume of the contrast agent. As a result, edema does not change Gd-DTPA-enhanced T1 relaxation times of the viable myocardium.

Analysis of Variance↗

PubMed2004

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. T1 relaxation times of the myocardium were measured with a TurboFLASH inversion-recovery sequence. Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) (0.05 mmol/kg body wt) was then injected as a bolus into the aortic perfusion line. The first pass of the contrast agent through the heart was followed using the interleaved T1-T2* imaging sequence. Once the concentration of the contrast agent was in an equilibrium state, T1 relaxation times were measured again. It was found that the percentage recovery of T2* intensity (PRT2*) at the maximum T1 intensity measured during the first pass of the contrast agent with the interleaved T1-T2* imaging was significantly higher in infarcted myocardium than in normal myocardium. Moreover, the regions showing a high T2* percentage recovery on PRT2* maps matched well with the infarcted myocardium demarcated with triphenyl tetrazolium chloride (TTC) staining. We therefore conclude that infarcted myocardium can be delineated using the interleaved T1-T2* imaging method.

Animals↗

PubMed2003

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. Phosphorus 31 magnetic resonance spectroscopy was used to determine the efficacies of the cardioplegic techniques in sustaining myocardial energy metabolism. RESULTS: At the same flow rate, the number of colored microspheres delivered to the capillaries by retrograde cardioplegia (15 +/- 1 microspheres/mm2) was significantly lower than that delivered by antegrade cardioplegia (29 +/- 2 microspheres/mm2). Furthermore, only 19% +/- 3% of the colored microspheres delivered to the capillaries by retrograde cardioplegia were found in the arteriolar portions of the capillaries, whereas most (80% +/- 3%) remained in the venular portions. Moreover, magnetic resonance images showed that contrast-enhanced signal-time courses obtained from different regions of the myocardium during retrograde cardioplegia varied significantly. Localized phosphorus 31 spectra showed that retrograde cardioplegia required a higher flow rate than did antegrade cardioplegia to sustain normal myocardial energy metabolism. CONCLUSIONS: We conclude that retrograde cardioplegia provides significantly less capillary flow than does antegrade cardioplegia. Its microvascular perfusion varies significantly among the various small areas of the myocardium. As a result, its efficacy in sustaining normal myocardial energy metabolism is lower than that of antegrade cardioplegia.

Animals↗

PubMed2002

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. RESULTS: Observing contrast-enhanced R(1) or R(2)* rates (1/T(1) or 1/T(2)* times, respectively) early after contrast injection did not fully differentiate viable from nonviable myocardium. T(2)* recovery at maximal T(1) signal intensity, measured using simultaneous T(1) and T(2)* imaging, displayed a significantly different percentage recovery (P < 0.05) among normal (30.5 +/- 2.4% of baseline value), reperfused infarcted (63 +/- 7.2%), and low-reflow infarcted (90 +/- 2.8%) myocardium. CONCLUSION: Simultaneously monitoring both T(1) and T(2)* signal intensities may help in the assessment of myocardial injury.

Analysis of Variance↗