Posted: April 13th, 2015

Coronary Artery Disease – BypassAccording to the National Institute of Health, coronary artery disease (CAD is the “leading cause of death in the United States for men and women”.

Coronary Artery Disease – BypassAccording to the National Institute of Health, coronary artery disease (CAD is the “leading cause of death in the United States for men and women”.

When coronary arteries become diseased, usually as a result of atherosclerosis, the build up of plaque on the inner walls of vessels, the result is defined as CAD.  The plaque itself and the inflammation resulting from the plaque causes the arteries to narrow or stricture.  Signs and symptoms vary upon the degree of stricture, however, a complete blockage can result in a heart attack and/or ischemia due to lack of oxygen to the cardiac muscle.
If left untreated, CAD can lead to heart attack, heart failure or arrhythimas, abnormal beating rhythms of the heart.  Screening tests for CAD include, electrocardiogram, exercise stress test, radionuclide stress test, stress echocardiography, pharmacologic stress test, computerized tomography (CT) scan, and coronary angiography.
Current treatment for coronary artery disease includes:
•    Lifestyle changes
o    Smoking cessation
o    Changes in diet
o    Exercise
o    Weight loss
o    Stress reduction
•    Drugs
o    Cholesterol medication
o    Aspirin
o    Beta blockers
o    Nitroglycerin
o    ACE inhibiters and ARBs
•    Medical intervention
o    Angioplasty and stent placement
o    Coronary Artery Bypass surgery
•    Nonconventional methods
o    Fish oil and Flaxseed

My topic focuses on coronary artery bypass surgery or coronary artery bypass grafting (CABG).  According to the American College of Cardiology (ACC) and the American Heart Association (AHA) the indications for a CABG include left main coronary artery stenosis greater than 50%, 3-vessel disease in asymptomatic patients or patients with mild or stable chest pain, 3-vessel disease with proximal LAD stenosis in patients with poor left ventricular function, 1 – 2 vessel disease in patients with stable angina, significant ischemia evident with noninvasive testing, disabling angina, evidence of ongoing ischemia, poor left ventricular function.  Contraindications for a CABG include asymptomatic patients who are at low risk of myocardial infarction (MI), patients who will receive little to no benefit from the procedure, and the elderly.
Traditionally a CABG is performed through open-chest surgery, and requires removal of the diseased portion of the coronary arteries.  The diseased portion is bypassed with healthy artery or vein grafts to help improve the blood flow to the heart.  A CABG procedure may or may not require the use of a heart-lung machine, depending on whether the procedure is done through the open-chest approach or minimally invasive approach.  The minimally invasive approach has developed over the years.  In the 90s the minimally invasive direct coronary artery bypass (MIDCAB) was developed which utilized a small thoracotomy incision.  This technique has its limits (it is best only for single vessel bypass procedures) that do not allow for widespread utilization for CABG.  The off pump coronary artery bypass grafting procedure (OPCAB) evolved from the MIDCAB.  This technique allowed for mutli-vessel bypass procedures and allowed for continuous beating of the heart negating the necessity of the heart-lung bypass machine which improved patient outcomes.  The approach is through a median sternotomy incision.  Currently the procedure has evolved into an even more minimally invasive technique or miniCABG procedure utilizing robotic technology.
I intend to explore the possibilities for improvement of minimally invasive CABG procedures.
Poston, R., Tran, R., Collins, M., Reynolds, M., Connerney, I., Reicher, B., Zimrin, D., Griffith, B., and Bartlett, S.  (2008).  Comparison of economic and patient outcomes with minimally invasive versus traditional off-pump coronary artery bypass grafting techniques.  National Institute of Health.nihms88954.pdf

2. Heart Failure
Heart Failure is a chronic condition requiring constant supervision and care due to its life-threatening progressive nature. The condition is mainly caused by inadequate pumping of blood to other parts of the body. The heart’s main function in the body is to supply organs with blood carrying oxygen and nutrients through continuous synchronized contractions of its ventricles. In a normally functioning heart, the ventricles should pump out about 50-75% of the total amount of blood. This percentage, commonly referred to as “Ejection Fraction” can provide an early indication of heart failure if below 35%.1 With an estimated 825,000 patients diagnosed each year, heart failure is considered one of the prominent diseases affecting the US population, the number expected to rise to more than 8 million people by year 2030.2
Heart failure may result from 3:
1.    Inadequate pumping of blood, ultimately causing thinning and enlargement of the ventricles, in which case it is called systolic Heart failure,
Stiffening of heart muscles which prevent them from filling up with blood. More common in elderly patients, the condition is referred to as diastolic Heart Failure.  In both cases, enlargement and thickening of the heart muscles may eventually lead to Congestive Heart Failure. Symptoms of heart failure range from shortness transplantation.
Initial approach based on the treatment algorithm from the European Heart Journal1 is the adoption of the general measures and initiation of pharmacological therapy that includes oral anticoagulant drugs, diuretics to reduce fluid retention, supplemental oxygen for hypoxaemia and digoxin to treat refractory right heart failure and/or supraventricular arrhythmias. Vasoreactive patients should be treated with calcium channel blockers. Non-responders can consider treatment with endothelin receptor antagonist (ERA) or a prostanoid. The choice of the drug is dependent on a variety of factors, including the availability in country, route of administration, side effect profile, patient’s preferences and physician’s experience.
Combination therapy may be considered for patients who fail to improve or deteriorate with first-line treatment. Balloon atrial septostomy and/or lung transplantation are indicated for refractory PAH or where medical treatments are unavailable.
1.    Guidelines on diagnosis and treatment of pulmonary arterial hypertension: The Task Force on Diagnosis and Treatment of Pulmonary Arterial Hypertension of the European Society of Cardiology
2.