2011-08-012024-05-14https://scholars.lib.ntu.edu.tw/handle/123456789/658884摘要：題目：心肌梗塞後四維心肌纖維排列的變異與左心室功能之探討：一個應用擴散張量磁振造影技術的動物實驗。TOPIC: Derangement of Four-Dimensional Myocardial Fiber Orientation afterMyocardial Infarct and Its Clinical Implication on Left Ventricular Function– an AnimalStudy with Diffusion Tensor Magnetic Resonance Imaging研究背景及目的：左心室收縮除了一維與二維肌肉纖維的線性及環狀收縮以外，還有三維幾何上的形變以增加收縮力及舒張力。此乃根源於左心室肌肉特殊的排列結構。理論上心尖瘤病患因為心尖部缺血壞死造成纖維化，將導致心室肌肉排列異常，進而影響心室收縮及舒張功能。MRI的擴散張量影像 （diffusion tensor imaging, DTI）技術曾被應用於檢查活體心臟肌肉的纖維排列。後續研究顯示心肌梗塞病患其中層心室壁橫截面之內層斜向纖維減少，但有趣的是，某些相鄰於梗塞區的上層或下層區域，其心肌纖維排列亦受影響，其原因至今仍不明。本計畫將研究心肌梗塞動物（兔）與對照組之左心室四維（立體三維加上時間一維）的心肌纖維束排列的變異，以及這些纖維排列變異之臨床意義。研究方法：預計40隻（30隻實驗組，10隻對照組）3公斤紐西蘭公白兔經氣管造口全身麻醉後進行左前胸開胸術，綁扎左冠狀動脈以產生心肌梗塞。6週後接受心臟超音波及3Tesla-MRI檢查以確定心肌梗塞範圍，心臟擴大，以及心臟功能。再插入Millar導管測量左心之壓力-體積關係。後注射高量鉀離子心臟痲痹液或細胞內心臟痲痹液造成舒張期心痲痹（diastolic cardiac arrest），取出心臟，進行高磁場核磁共振造影檢查，以擴散張量影像（DTI）觀察心肌纖維。再注射生理食鹽水及高鈣離子溶液，使心臟產生收縮態，重複前述擴散張量磁振造影檢查。根據前項DTI-MRI資料，計算出立體纖維排列（tractography），方向不一致度（anisotrophy），擴散長度（trace-ADC）等重要參數。比較梗塞組與對照組之收縮期及舒張期的各組數據之差異，以明瞭心肌梗塞後心肌纖維排列之變異。與超音波，壓力-容積曲線圖，以及3T-MRI心臟檢查結果相比較，以明瞭這些肌纖維排列變異與心臟功能變異之關係。<br> Abstract: 題目：心肌梗塞後四維心肌纖維排列的變異與左心室功能之探討：一個應用擴散張量磁振造影技術的動物實驗。TOPIC: Derangement of Four-Dimensional Myocardial Fiber Orientation afterMyocardial Infarct and Its Clinical Implication on Left Ventricular Function– an AnimalStudy with Diffusion Tensor Magnetic Resonance ImagingBackground:The special three-dimensional architecture of left ventricular muscle fibers makes theventricle to contract in a particular and efficient way, resulting in an increasedsystolic and diastolic ability. Left ventricular apical aneurysm is caused bymyocardial ischemia and fibrosis and is associated with extensive derangement of thearchitecture of myocardial fibers, which will result in a loss of ventricular systolicand diastolic efficiency.MRI diffusion tensor imaging (DTI) technique had been used in in-vivo study ofmyocardial fiber architecture. Another study had applied it to myocardial infarctpatients and revealed a decrease in sun-endocardial oblique fiber not only in theinfarct area, but also in adjacent areas. The reason and the implication of this findingare not fully understood.The aim of the present study is to study the derangement of four-dimensional(three-dimension plus a time dimension) ventricular myocardial architecture in aninfarct animal model (rabbits) and its clinical implication.Material and Methods:40 New Zealand rabbit (3-4Kg), 30 in experiment group, 10 in control group, isenrolled in the study. The rabbit is anesthetized and intubated via a trachostomy.Coronary arteries are ligated via an anterior thoracotomy wound. Two months later,the rabbit receives echocardiography and 3-Tesla MRI to evaluate the territory ofinfarct and the resulting ventricular dilation and function. Millar catheter is insertedinto left ventricle to evaluate pressure-volume relationship. High-concentrationpotassium or intracellular cardioplegic solution is infused into aorta to achievediastolic cardiac arrest. The heart is then removed and sent to 7-Tesla MRI for DTIstudy. After the first DTI-MRI scanning, normal saline and high-concentrationcalcium solution is infused into aorta to achieve systolic cardiac contracture. AnotherDTI-MRI scanning is performed.Fiber tractography, fiber anisotrophy, and average diffusion distance (trace-ADC) inboth systolic and diastolic phases are derived from DTI-MRI data. All the data iscompared with echocardiographic data, pressure-volume relationship, and ventricularmotion data from 3T-MRI to evaluate the impact of the derangement of ventricularfiber orientation on the ventricular performanc