Cardiovascular Surgery,Hiroshima University Hospital

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Hiroshima University Surgery1 Cardiovascular Surgery Group
Kasumi1-2-3,Minami-ku,Hiroshima
734-8551JAPAN
TEL:+81-82-257-5468
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　　# Symptoms of valvular diseases

　　For example, mitral valve diseases cause congestion of the blood in the lung.  It leads to shortness of breath, dyspnea.  In addition, blood stasis induces arrhythmia, atrial fibrillation.  This arrhythmia occasionally causes thrombus formation in the left atrium, which leads to thromboembolism.  In many patients, stroke is the first symptom of mitral valve diseases.  In aortic stenosis, the left ventricle is exposed to pressure overload because the outlet is very narrow.  Sudden death can occur due to life-threatening arrhythmia induced in the left ventricle.  In the tricuspid valve disease, blood is congested in the right atrium.  This causes blood congestion in the body and leads to edema of face and legs. 

　　# Diagnosis of valvular diseases

　　Although valvular diseases are often asymptomatic, they can be recognized early by auscultation, chest X-ray, or electrocardiography.  When one has heart murmur on auscultation, cardiomegaly on chest X-ray, or overload on the ventricle or arrhythmia such as atrial fibrillation, echocardiography is often the first assessment toward the definite diagnosis.Echocardiography is painless, noninvasive, and feasible at the out-patient clinic.  It can clearly demonstrate size and movement of each of four cardiac chambers, thickness or movement of valves, and severity of valvular regurgitation.  It takes only 10 to 20 minutes for routine echo examination.  It is an essential modality for diagnosis of valvular diseases. 

　　#Surgical treatment of valvular diseases
 　 Standard surgical treatment of valvular diseases is valve replacement.  Diseased valve is resected and replaced with a valve prosthesis, artificial valve, into the original site. 





There are two kinds of valve prosthesis: one is mechanical valve, composed of alloy of metal and carbon, the other is bioprosthesis, made of biomaterial which is extracted from cow or pig.Each has merit and demerit for each patient.





 　　Recently, valve repair is getting popularity in addition to valve replacement.  In this technique, the valve is repaired instead of being removed.  It is necessary to consider whether this method is applicable to each individual patient, based on the condition of the valve, general condition of the patient, associated valvular diseases, and so on. 

　　Result of valve repair varies according to the technique of surgeon. This treatment is still challenging because the mitral valve of the arrested heart appears differently from that in the beating heart. Therefore, simple inspection is not adequate for designing the repair and regurgitation may remain after the heart starts beating.
　
　　We assess the mitral valve by means of transesophageal echocardiography and recognize the shape and special relationship of valve leaflets while the heart is beating and design the surgical procedures for each individual patient. Immediately after the heart starts beating, mitral regurgitation is checked with transesophageal echocardiography. Therefore, no patient finishes surgery with residual regurgitation.

　　# Catheter treatment of valvular disease
　
　　Challenges have begun to treat the valvular diseases without surgery but with catheter through the vessels. Although a number of treatments have been developed, most of them has not reached the level of adequate results with safety. The only catheter treatment currently available is catheter intervention for mitral stenosis, called PTMC (percutaneous transvenous mitral commissurotomy), where the narrow valve is dilated with balloon.





　 A specially designed catheter is inserted from the vein in the groin and is advanced to the heart. It penetrates the interatrial septum and reaches the mitral valve. It is passed through the mitral valve and the balloon is dilated below and above the valve, then in the valve.

　 This procedure is usually performed under fluoroscopic guidance. However, because the wall of the heart is not visible with X-ray, catheter procedures can injure the wall of the heart. We use transesophageal echocardiography as well as fluoroscopy for guiding the catheter manipulation in order to to minimize the occurrence of complication. The patient is anesthetized during this procedures.

　　# When to treat the valvular diseases
　
　　Twenty years ago, surgical treatment of valvular diseases was not so safe as it is now. So, they were treated with drugs as long as possible and surgery was the nearly the last option. Because of heart failure at the time of surgery, the risk of surgery was much higher.
　
　　However, cardiac surgery has become safer and more certain these 10 years. A large amount of blood transfusion and long hospital stay before has changed to no transfusion and early discharge in many patients. Now we recommend surgical treatment before severe heart failure and arrhythmia develops. It fascinates early recovery after surgery with preserved cardiac function. It is time of "early diagnosis and early treatment" also for cardiac surgery.　
　
　　Furthermore, atrial fibrillation often associated with valvular diseases can be surgically changed to normal rhythm in most patients recently. This new treatment has reduced annoying arrhythmia, palpitation, and concern of stroke (described later). 　

　2) ANGINA PECTORIS AND MYOCARDIAL INFARCTION

　　　(ISCHEMIC HEART DISEASE)

　　# What is coronary artery

　　The heart keeps working, while one sleeps, expelling blood to the body. In order to work tirelessly all the time, the myocardium necessitates fuel, that is nutrition and oxygen. These are delivered to the myocardium through the coronary artery. It is on the surface of the heart, diverging and distributing to the entire portion of the heart. There are two coronary arteries: right coronary artery and left coronary artery. It is called as coronary because the shape looks like "corona".





　　# What is angina pectoris

　 When the coronary artery is diseased with atherosclerosis and others and the blood is not adequately delivered, the myocardium of downstream region faces a shortage of oxygen and nutrition, especially when one exercises or gets excited and the myocardium necessitates more nutrition. Chest oppression or squeezing pain appears (angina). This is angina pectoris. It resembles the leg pain when the it has fallen asleep. As the blood flow recovers, the pain is relieved. Pain of angina pectoris usually relieves within 10 minutes.

　　# What is myocardial infarction

  When the coronary artery is suddenly occluded, blood is exhausted in the downstream myocardium.  With severe angina, the myocardium faces extreme suffocation.  The angina does not relieve after 10 minutes.  As the legs becomes flaccid with tingling pain, the myocardium presents with similar event. 

The myocardium becomes unable to contract and cannot work as a pump (pump failure). Abnormal excitation of myocardium like tingling pain induces lethal arrhythmia, ventricular fibrillation. The whole ventricle fibrillates and cannotcontract at once.These two cause paralysis of the heart."Death on heart attack"is mainly caused by acute myocardial infarction.

  Depletion of blood supply to the myocardium is responsible for both angina pectoris and myocardial infarction, which are called as ischemic heart disease. 

　　# Treatment of ischemic heart diseases 　

  Treatments for angina pectoris and myocardial infarction are aimed to deliver an adequate amount of blood to the myocardium under ischemia.  There are medical treatment, catheter intervention, and surgical treatment. 

　1) Catheter treatment

  A specially designed catheter is inserted into the artery of the groin or arm and advanced to the coronary artery under fluoroscopic guidance.  It is passed through the diseased portion of coronary artery.  As the balloon is inflated, the atheroma (debris caused by cholesterol etc.) is compressed and the lumen of coronary artery is restored.  This treatment enables the blood to reach the ischemic myocardium and relieves symptoms of angina pectoris and myocardial infarction.  This treatment is called as PTCA (percutaneous transluminal coronary angiography). 
　

  The coronary artery can become narrow after balloon inflation due to elasticity or rigidity of the wall.  Occasionally the intima of coronary artery is damaged with balloon.  In these cases, stent, cylindrical metal mesh, is inserted into the coronary artery and pressed toward the arterial wall, to maintain the dilated lumen and to prevent acute formation of thrombus.  This treatment is called as coronary stenting. 

　2) Surgical treatment 　

  　There are occasions where the coronary artery becomes stenotic repeatedly in spite of PTCA or stenting or such treatment is risky because the lesion is at the main orifice of coronary artery.  In such cases, ischemic heart diseases are treated surgically: CABG (coronary artery bypass grafting).  In CABG, the portion of diseased coronary artery is not directly treated, but new route of blood to the ischemic region is made.  This surgery makes detour or bypass, and is called as bypass surgery. 





　　The vessel for delivering the blood is called as graft. The following vessels are used as graft.

　- internal thoracic artery: artery behind the sternum

　- great saphenous vein:vein under the skin from the inner 　malleolus to the groin

　-right gastroepiploic artery: artery that supplies blood to　the stomach

　- radial artery: artery at the thumb side of the arm, where one can feel pulse

　These vessels are harvested and are utilized for the heart.


　　# Off-pump bypass and On-pump bypass
　
　　In CABG, meticulous fine technique is required to anastomose the vessels of 1 to 2 millimeters. A loupe is usually used to avoid stenosis or occlusion of anastomosis. In order to achieve a safe and secure anastomosis, it is best to proceed the surgical procedures on the arrested heart (motionless heart): on-pump bypass. However, this process occasionally causes stroke due to embolism of atheroma derived from the aortic wall. In many patients who necessitate CABG, atherosclerosis is often present on the aortic wall.

　　Recently, a new technique has become popular: anastomosis with the heart beating. This procedure has reduced the risk of stroke. However, anastomosis is technically difficult and slightly lower the quality of anastomosis. In off-pump bypass, one graft is often anastomosed to more than two sites. Once the graft is occluded for any reason, multiple areas can be affected.

　　In order to solve this problem, we routinely assess the aortic wall with computed tomography and transesophageal echocardiography and determine whether the conventional method can be safely performed. If the aortic wall has no significant atherosclerosis, anastomosis is done with arrested heart or with reduced beating under assistance of cardiopulmonary bypass (on-pump beating). If the aortic wall is not clear, off-pump procedures are done. The basic principle is that we take priority to the quality of anastomosis while avoiding complication as completely as possible.

　　# Clue to early diagnosis

　　Factors that possibly cause ischemic heart disease include hypertension, hyperlipidemia, diabetes mellitus, smoking, and obesity. When you have symptoms such as squeezing pain or chest oppression when you walk upstairs, run, or lift a heavy stuff, early check-up at the hospital is strongly recommended. These symptoms appear when one has ischemic heart disease or aortic stenosis. It is important to have an appropriate assessment because delay in early diagnosis may lead to considerable events. These two diseases are also common among people who have had hemodialysis for years and can be causative to sudden death of these people. Angina is not apparent in those with diabetes mellitus even when they have advanced lesion of coronary artery or history of myocardial infarction.



　　　B. ARRHYTHMIA AND HEART FAILURE


　　We have worked in a team setting with Cardiologists in order to introduce the state-of-the-art treatment of arrhythmia and heart failure, and have provided the latest treatment and proceeded the research and development for future treatments. Thus, we keep functioning as so-called HIROSHIMA ARRHYTHMIA CENTER.

　　Arrhythmia includes those with lower rate (bradyarrhythmia) and those with higher rate (tachyarrhythmia). Both of these impairs cardiac function as its severity increases and may be life-threatening. Not only arrhythmia but valvular or ischemic heart diseases can lead to chronic heart failure. Recently pacing therapy has been applied to treatment of heart failure as well.

　1) generation of normal heart rhythm

First, generation of normal heart rhythm in the heart is summarized.Please refer to this normal condition when reading the later description of various arrhythmias.

The heart of composed of 1)myocardium, 2) fibrous portion as skeleton, 3) valve, and 4) specially developed myocardium that works like the nerve.The last one generates active excitation in the heart that conducts through the heart and make a pace of heart beat.The starting point is sinus node (sinoatrial node). Excitation arises here at a rate of 60 to 80 times a minute.This is the origin of　heart beat.Excitation is conducted through the wall of right and left atrium and induces atrial contraction.The blood that has returned from the body or lung is pushed into the right and left ventricle.Excitation reaches the atrioventricular node.It is like a rest station.While the conduction of excitation has a rest, the blood moves into and fills the ventricles. 　

　2) ARRHYTHMIA WITH LOWER PULSE RATE

　　# What is bradyarrhythmia?　　　　　　　　　　　　　　　　　

　　If conduction of excitation is blocked at any portion of this route, the pulse rate becomes lower. Popular diseases include:

　1) sick sinus syndrome

　2) atrioventricular block

　3) bradycardic atrial fibrillation

　　Sick sinus syndrome is caused by malfunction of sinus node, origin of heart beat, and presents with lower pulse rate. Atrioventricular block occurs when conduction of excitation is blocked at the diseased atrioventricular node. Although pulse is generated instead at the vicinity of atrioventricular node, the rate is as low as 30 to 40 per minutes. In atrial fibrillation, conduction in the atrium is disorganized. Excitation is randomly conducted to the atrioventricular node and thus generates irregular heart beat. As the conduction to the node is slightly reduced, pulse rate becomes low: bradycardic atrial fibrillation.

　　All of these diseases present with lower pulse rate of 30 to 40 a minute or interruption of pulse for several seconds.When the pulse rate becomes low, one feels fainting or blackout or occasionally tiredness.When heart beat interrupts for several seconds, one may fall unconscious.

　　To our disappointment, it is difficult to reliably increase the pulse rate with drug. The most reliable therapy is pacing therapy.

　　# Pacemaker
　
  Pacemaker stands for MAKER (one that makes) of PACE (regular rhythm). It generates cardiac rhythm with electrical stimulation when the rhythm becomes irregular or inadequate.





　　 Pacemaker is composed of generator which is implanted under the skin of the chest and lead which connects the generator and the heart.  Pacemaker keeps watch on the excitation in the heart (electrocardiography).  Whenever it abnormally drops, pacemaker delivers electrical stimulation to the heart and make it contract.  Thus, pacemaker prevents dropout of heartbeat. 

　　#  Pacemaker implant





 　　Pacemaker is implant surgically.  We usually implant the pacemaker in the operating room.  Surgery is done under local anesthesia.  It takes 1 to 2 hours.  The patient enters the hospital the day before surgery.  After implant, one can take a meal on the day and walk around.  Suture is removed and the generator is checked on the seventh day and the patient is discharged. 

　　#What is biventricular pacing

　　# Symptoms of aortic aneurysm

 　　Thoracoabdominal aortic aneurysm, that is aneurysm extending from thoracic to abdominal aorta, is treated with replacement of aneurysm with vascular graft.  However, spinal cord damage due to ischemia can be complicated with this surgery.  This is because an important artery that supplies blood flow to the spinal cord can arise from this replaced portion of aorta.  The intercostal or lumbar artery of the aneurysmal aorta is usually sutured.  In many patients, an important one arises around the diaphragm, called as Adamkiewicz artery. 




　The blood flow for the spinal cord is supplied from three levels: around the neck, diaphragm (Adamkiewicz artery), and lumbar.Because these three arteries often has poor communications to each other, occlusion of Adamkiewicz artery can lead to permanent damage of spinalcord that presents with araplegia (palsy of lower body).One is obliged to have life on the wheelchair for the rest of life.Sense of urination and evacuation is also lost.Often decubitus develops on the buttock with considerable infection.

　　Incidence of such tragedy is reported to be several to 20 %. If the aneurysm is left untreated, it will blast soon. Emergency operation for ruptured aneurysm is complicated with higher risk of complications. Many scientists have searched for solution for this problem in all over the world. This disease is not so simple that can be treated in any hospital.

　　　Current strategy for this disease is described.


　　a) Identification of Adamkiewicz artery with CT

　　The Adamkiewicz artery is searched with preoperative CT and is found in 80 to 90% of patients. Location of this artery is confirmed before surgery so that it is identified during surgery. However, this artery cannot be visualized with CT.


　　b) Motor-evoked potential monitoring

　　We always have a concern that CT might not find every artery to be identified. Thus, we use a special monitor, called as motor-evoked potential (MEP) monitoring during surgery.

　　An electrode is inserted from the back into the vicinity of spinal cord the day before surgery. During surgery, an electrode is placed on the head and electric stimulation is given. Excitation is conducted from the brain down to the spinal cord. This signal is recorded with the electrode near the spinal cord.





　　If the Adamkiewicz artery is unintendedly injured during surgery or blood flow of this artery with unusual course is blocked, the spinal cord becomes ischemic and conduction of excitation is blocked. When MEP is reduced, this indicates that something goes wrong. We experienced several patients that escaped the spinal cord damage with this monitoring.





　　c) cerebrospinal fluid drainage

　　Even if the Adamkiewicz artery is preserved, the spinal cord suffers from a certain degree of hypoperfusion. The spinal cord can be swollen for several days after surgery. Because the spinal cord is surrounded by a duct (spinal canal) made of rigid bone, swollen spinal cord is compressed by the surrounding tissue or fluid and becomes ischemic. Within several days of surgery, palsy of lower body can occur. To prevent this, a fine tube is placed into the spinal canal through the back for letting the fluid out. This is called as cerebrospinal fluid drainage. Several patients escaped palsy with this treatment.

　　With all these efforts, the incidence of paraplegia in our hospital is as low as 5% (much lower recently). However, it is not perfect yet. Even a top level hospital in the world has 1 to 2% of incidence. Investigation is still going for achieving a safer surgery. While we treat the patients with best possible method and technology, clinical data are being collected for analysis toward a better certainty. In addition, we develop further methods with animal studies. Some of new methods may be applied to the clinical use in the near future. We believe that such attitude and efforts are mandatory for those who treat the thoracoabdominal aortic aneurysm. This is a typical disease that treatment should produce something new for the future.

　　Even with novel techniques, emergency operation can be accompanied with higher incidence of complication because preoperative preparations are not sufficient. In this sense, what is important is early detection and early treatment.


　　　5. Strategy for bowel ischemia in aortic dissection

　　This is another problem to be solved and some measures are needed. When internal membrane occludes the artery that supplies the bowel (superior and inferior mesenteric artery), bowel ischemia occurs. If blood flow cannot be restored within several hours, the bowel becomes necrotic. It leads to peritonitis, hepatic failure, or renal failure, resulting to death within several days.

　　On the other hand, however, risk of aortic rupture necessitates replacement of aorta early. One should determine which should be treated first. However, diagnosis of bowel ischemia is not easy. The CT images obtained in the previous hospital are not necessarily of sufficient quality to make a diagnosis of ischemia. Usually the condition of the patient is not stable enough to take another CT examination. What is worse, bowel ischemia can newly occur in the operating room often due to extracorporeal circulation (artificial perfusion). It is impossible to have a CT examination in such a situation.

　　We developed a novel method of making diagnosis of bowel ischemia by using TEE. The abdominal aorta and visceral arteries were considered to be out of the range of visualization with TEE. However, we have found that some additional techniques have enabled to visualize the superior mesenteric artery in the majority of patients (over 90%) and reported to the scientific journal in 1999. Observation is feasible during surgery without interrupting surgical procedures and repeatedly or continuously without use of contrast media.





　　Toward the future

　　When we treat any disease, we do not just cure the patient but always search for any better treatment. Every treatment should produce any advancement in medicine: we believe this is important. New ideas and findings are reported in the scientific meetings and journals not only in Japan but in international base to confirm that our output is not a complacence.