Thursday, December 9, 2010

CORONARY ARTERY BYPASS GRAFT

video source : 2008 Nucleus Medical Art. All Rights Reserved

A coronary artery bypass graft or CABG is performed to improve circulation to heart muscle. In people who severe coronary artery decease. In this procedure a healthy artery or vein from another part of the body is connected or grafted to the blocked coronary artery. The grafted artery or vein bypass the blocked portion of coronary artery carrying oxygen riched blood to heart muscle. One or more coronary arteries maybe bypass during the single operation. Before the surgery, an intravenous line would be started and you maybe given a medication to help you relax. CABG procedure are under general anesthesia which would put you to sleep for the duration of the operation. A breathing tube would be inserted through your mouth and into your throat that help you breath.

A catheter will be placed to your bladder to drain your urine. CABG surgery generally take 3 to 6 hours, during your conventional bypass surgery, your surgeon begins by making a decision in a skin over your breastbone. He or she will begin cut your breastbone and move your rib cage in order to get your heart. The after procedure, your circulatory system would be connected to cardial pulmonary bypass pump or heart lung machine. This machine temporally perform the function of your function of your heart and lung during the surgery, allowing your heart to be stopped while the surgeon sew the grafts in the place. One or two blood vessel, is typically used for the graft.

With the grafts securely emplace, your surgeon will use electrical signal to restore the heart beat and attach a temporary pacemaker to heart. Once, your heart is again beating normally the heart lung machine would be disconnetted. Your surgeon would wire the breastbone back together and sew the skin. A temporary drainage tube would be placed through the skin. Two other types of CABG procedures have recently been developed, Off-pump and Minimally invasive bypass surgery. Off-pump CABG just also called beating heart bypass grafting because the heart isn't stopped and heart lung machine isn't used. Instead a mechanical device is used to steady the part of the heart when grafting is being done. Surgeon performs minimally invasive bypass procedure using specially design instrument. This procedure sometime require a heart lung machine.

After surgery, you'll be taken to Intensive Care Unit (ICU). The activity of your heart would be carefully monitored. If necessary, the pacing wire would be used to temporary control your heart rate. The chest tube would be remained in place to drain excess blood and air from the chest cavity. Once you can breath on your own, your breathing tube would be remove and replace the oxygen mask. The bladder catheter would remain in place. As you recover over the next 3 or 4 days, all of these devices would be gradually removed.

The Hemodynamics of Vein Grafts: Measurement and Meaning

Christopher L. Skelly, MD, Shari L. Meyerson, MD, Michael A. Curi, MD, Francis Loth, PhD, and Lewis B. Schwartz, MD, Chicago, Illinois

INTRODUCTION

The first successful experimental venous bypass grafts were created by Nobelist Alexis Carrel in 1906 in the Hull Physiologic Laboratory (now Culver Hall) at the University of Chicago.1 Over the ensuing century, infrainguinal autologous bypass has become increasingly applied, and approximately 100,000 grafts are now created annually in the United States. The safety and efficacy of the procedure have improved markedly in recent years. In large series, the mortality from infrainguinal by- pass approaches 2%, with major morbidity including myocardial infarction, cerebrovascular accident, and renal failure estimated at about 7%.2 The risk of immediate graft failure and limb loss also remains at about 7%. Thus, the vast majority of patients enjoy a favorable immediate operative result and revascularization. However, the lifespan of the graft is highly variable and, despite the initial technical success, grafts fail in subsequent years at an alarming rate. For all grafts in all patients, the reported 5 year primary patency, secondary patency, and limb salvage rates are about 60, 75, and 85%, respectively.2 These patency rates continue to slowly decline over the next 5 years to 40, 45, and 50%. This incessant attrition of functioning vein grafts remains the most important and frustrating limitation of the procedure.


Considerable attention has been devoted to improving the long-term results of peripheral vein grafting, with special emphasis on proper patient selection and refinement of surgical technique. Although certain clinical factors, such as renal fail- ure3,4 and diabetes,4-6 have implications for perioperative morbidity and long-term survival, none have predictive value for graft patency. The only remotely reliable predictors of graft patency are de- rived from the anatomic and hemodynamic aspects of the reconstruction itself, such as the quality and origin of the conduit and its outflow bed. The purpose of this review is to discuss the available techniques for the characterization of the hemodynamic environment of infrainguinal autologous bypass grafts, and the potential dependence of graft pa- tency on its hemodynamic environment.

Sunday, November 7, 2010

Mixing through stirring of steady flow in small amplitude helical tube

A.N. Cookson, D.J. Doorly and S.J. Sherwin

Introduction


Almost 30,000 coronary artery bypass graft procedures are perfomed each year in the UK according to the British Heart Foundation, however over 50% of CABG fail within 10 years due to the development of neo-intimal hyperplasia.



#Coronary artery bypass surgery, also coronary artery bypass graft (CABG pronounced cabbage) surgery, and colloquially heart bypass or bypass surgery is a surgical procedure performed to relieve angina and reduce the risk of death from coronary artery disease. Arteries or veins from elsewhere in the patient's body are grafted to the coronary arteries to bypass atherosclerotic narrowings and improve the blood supply to the coronary circulation supplying the myocardium (heart muscle). This surgery is usually performed with the heart stopped, necessitating the usage of cardiopulmonary bypass; techniques are available to perform CABG on a beating heart, so-called "off-pump" surgery.

#Intimal hyperplasia is the thickening of the Tunica intima of a blood vessel as a complication of a reconstruction procedure or endarterectomy. Intimal hyperplasia is the universal response of a vessel to injury and is an important reason of late bypass graft failure, particularly in vein and synthetic vascular grafts.

Similiarly, arterio-venous shunts constructed from ePTFE are prone to occlusion by thrombosis and intimal hyperplasia.
In the US alone there are 175,000 ePTFE grafts used for permenant vascular access, with the 1 and 2 year primary patency rates currently at 50 and 25% respectively.



Consequently, much research has been conducted in the past few decades to design drafts that will remain patent for far longer, ideally longer than the life-span of patient.


A promising avenue of this research, initiated by Caro and co-authors, is to use out-of-plane geometry that induce fully three-dimensional, physiologically realistic swirling flows, and produce more uniform wall share stress distributions. However in a clinical environment, such geometries cannot be guaranteed to be preserved after wound closure. Greater control of geometry is possible with vascular prostheses, with small amplitude helical tubes being proposed. The helical geometry induces the necessary swirling flow, whilst also being mechanically robust, and has undergone preliminary in vivo trials, and subsequently a preliminary clinical study by Huijbregts el al. Caro et al. hypothesized that the in-plane mixing induce by the helical geometry and the more uniform WSS distribution are responsible for preventing graft occulasion from thrombosis and neo-intimal hyperplasia.

Likewise a new design of arterial stent has been proposed which when inserted in the host artery and expanded, enforces a helical tube boundary at the artery wall. This is an alternative procedure to the helical bypass graft, but the operating conditions, e.g Reynolds number, will be comparable to those of bypass graft. It is to be emphasized that the benefits of helical geometry in vascular conduits have yet to be firmly estasblished, although they appear promising. The range of possible configurations is large, and how the hemo-dynamics responds to changes in geometric parameters has not been studied in detail.


Systematic investigation of the effects of helical geometry on the hemodynamics are needed, not only to inform potential design of prostheses and surgical vascular reconstructions, but to improve our understanding of normal vasculature. As pointed out by Zabielski and Mestel, a helical pipeserve the idealization of many arterial geometries. The mechanisms governing mixing in such geometries may provide insiht into cardiovascular diseases such as atheroclerosis, which are thought to be linked to wall shear stress and wall transport. These consoderations provide the motivations for the work described below, in which a range of small amplitude helical geometries, representative of possible prosthetic vascular configurations or native tortous arteries are the subject of studies of flow structure and mixing.



#arterio-venous-A/V

#shunt- a hole or passage allowing fluid to move from one part of the body to another

#stent- is an artificial 'tube' inserted into a natural passage/conduit in the body to prevent, or counteract, a disease-induced, localized flow constriction. The term may also refer to a tube used to temporarily hold such a natural conduit open to allow access for surgery.

#hemodynamics- meaning literally "blood movement" is the study of blood flow or the circulation

#prostheses- a prosthesis, prosthetic, or prosthetic limb (Greek: πρόσθεσις "addition") is an artificial device extension that replaces a missing body part.

#tortuous- full of twists and turns.

Wednesday, February 24, 2010

SuccesS

SuccesS


There are some things success is not, it's not fame, it's not money or power.


Success is waking up in the morning, so excited about what you have to do that you literally fly out the door,
it's getting to work with people you love.


Success is connecting with the world and making people feel.


It's finding a way to bind together people who have nothing in common but a dream.


It's falling asleep at night knowing you did the best job you could.


Success is joy and freedom and friendship.


And success is LOVE ..

Tuesday, February 23, 2010

Khas buat insan yang bernama Nur Syazwani binti Muhammad

orang kata cinta itu buta,

tapi saya kata cinta membuatkan kita boleh melihat jauh ke dalam hati,

cinta tak perlukn mata,

tak perlukan telinga,

cinta cuma perlukan hati ...



MusicPlaylist
Music Playlist at MixPod.com

Wednesday, February 17, 2010

CFD Practice : Modeling Transient Compressible Flow

tue,2010 16th Feb

I modeled the transient flow of air through a nozzle. You learned how to generate a steady-state solution as a initial condition for transient case, how to set solution parameters for implicit time-stepping.

I also learnt how to manage the file saving and graphical postprocessing for depedent flows, using file autosaving to automatically save solution information as the transient calculation proceeds.

Finally, I learnt how to use ANSYS FLUENT's solution animation tool to create animations of transient data, and how to view the animations using the playback feature.

Given Problem :-

Flow through a simple nozzle is simulated as a 2D planar model. The nozzle has an inlet height of 0.2 m, and the nozzle contours have a sinusoidal shape that produces a 20% reduction in flow area. Due to symmetry, only half of nozzle is modeled.


Figure


Solution Animation :-

video
Pressure of Nozzle


video
Mach number of Nozzle


Solution Graph :-

Scaled Residuals


velocity vectors colored by velocity magnitude (m/s)

Monday, February 15, 2010

CKD dalam pasaran automotif

CKD ataupun nama penuh Complete Knock Down adalah satu set kit part kenderaan yang didatangkan lengkap dan hanya tunggu untuk dipasang sahaja . Istilah ini berasal dari industri elektronik tapi kini dipakai jugak dalam bidang automotif .

Cara ni dah banyak di praktik dalam industri automotif kat Malaysia, bukan saje kereta tapi termasuk ler jentera , lori ker . Tokey2 automotif dh byk guna trick ni untuk elak cukai import kastam. Kahkah. Businessmen katakan. Tak leh jalan straight depa corner jalan laen. Produk terjual dgn baeknyer, duit masuk byk dr duit kuar = Untung !

Kalo korang nak tau , dgn ade nyer CKD ni. Part dari luar tapi pasang kt Malaysia maka tarak lagi tarif cukai sebagai cukai kereta import, yang ni btol2 untung kat diorg. Tp untung kat negara jgk ah biler leh bagi peluang kerja kat rakyat tempatan. Cukai ? tetap kena,tp kurang skit ah sbb diorg dh kasi bakti kt negara dgn bg peluang kerja utk rakyat tempatan. Disamping tu dapat la tempias teknologi diorg skit2.( Tak kan mau kasi sumer kot ~ ).

Kang ade jgk mitusbishi evo versi Malaysia naek atas jalan raya . Keliru jgk JPJ mahu kesan yang mana satu jepon mari yang mana satu Malaysian made. Sbb sekarang ni ade je proton waja dh bedah plastic jadi Mitsubishi evo 10. Evo soul for live katakan !

Untuk pengetahuan, bikin-bikin jgk. Kalo berubah muke tarak lulus jalan atas jalan raya ! Pendek kata leh wat ronda-ronda maen dlm tempat perumahan korang je ler. Mau tayang satu pekan, tak sampai tggu traffic light simpang kedua naek hijau. Lampu biru datang singgah tanpa diundang ( kalo tak uncle dr JPJ Diraja, ni sekor agi si Jokie maut kuda putih Honda VFR800 ABS atau Honda ST1300 Pan European. Ade hati mauk lari ke ? Luper kan je ler,skalik diorg hambat,skjp je ~ Kesudahan? Abeskan sendirik ~

CKD nyer part tak byk pn , setakat engine,transmisi gear dgn bateri jer, yang mana perlukan teknologi robotik dr negara asal dan handling dr tenaga mahir tp harga jadi mahal jgk skit berbanding kt negara asal sbb sumer import masuk mentah2. Part laen tempatan mari ler (bg menambah share tempatan dr share asing ). Biler wt camni sekarang baru leh declare produk tempatan dan cukai jd cukai tempatan je. Ade jgk syarikat yg tak nk dideclare sbg produk tempatan. Hanya dpt intensif kt cukai jer ah. Produk terjual, rakyat mampu beli,sedia peluang kerja dan dpt teknologi skit ( biar tak byk pn ) .

Syarikat automotif terlibat bknnyer nk sgt wt CKD ni,tp kalo tak wt, syarikat akn jadi lingkup sbb persaingan hebat dr car marker asing laen yg lama bertapak dan mendapat kepercayaan buyer di negara tersebut. Biler wt gini, harga kereta jd murah giler, maka ramai ah wat loan nk beli kereta diorg. Senang citer !