Acute Cardiovascular Disease2018-10-08T15:13:12-04:00

Acute Cardiovascular Disease

Cardiovascular diseases account for almost a third of all deaths in the world each year.

The two major causes of death from cardiovascular disease include heart attacks (also called acute myocardial infarction or AMI) and stroke. In these diseases, interruption of blood flow to the heart or the brain results in a loss of function in these vital organs, leading to tissue death in the region affected by lost circulation.

About 7.3 million people in the world each year experience a heart attack. This includes 790,000 in the U.S., 1.3 million in India, 1.84 million in Europe and 2 million in China.

There are two main types of AMI: ST-elevation myocardial infarction (STEMI) and non-STEMI (NSTEMI). STEMI is a “classical” type of heart attack during which one of the heart’s major arteries (one of the blood vessels that supplies oxygen and nutrient-rich blood to the heart muscle) is blocked. In NSTEMI, the blockage either occurs in a minor coronary artery or causes partial obstruction of a major coronary artery. While the symptoms can be the same as STEMI, the damage to heart will be far less extensive.

In developed countries, the majority of patients admitted for treatment are diagnosed with NSTEMI; these make up about over three-quarter of all AMI diagnoses in the U.S. and two-thirds in Europe. In developed countries, there has been a significant shift from STEMI to NSTEMI over the last two decades. This shift is now occurring in some developing countries like China.

IMPACT

About 7.3 million people in the world each year experience a heart attack.

  • 790,000 in the U.S.
  • 1.3 million in India
  • 1.84 million in Europe
  • 2 million in China

Key procedures for treating AMI

AMI is typically treated with one of two different procedures: cardiac artery balloon and stenting, also called cardiac angioplasty or percutaneous coronary intervention (PCI), and coronary artery bypass grafting (CABG). PCI is most prevalent, performed up to half a million times in the U.S. and over two million worldwide. This procedure involves inserting a catheter into a peripheral artery (typically in the groin or arm) and threading it up to the heart where the source of blockage is located. The catheter contains a balloon tip. Once the catheter is in place through the blockage, the balloon is inflated at the narrowed area of the coronary artery. This opens the artery by pressing the plaque or blood clot blocking the artery against the sides of the artery, restoring blood flow. This will also expand the size of the artery somewhat. In the majority of cases, a catheter is used where the balloon is surrounded by an expandable metal mesh called a stent. When the balloon inflates, the stent expands against the walls of artery. When the balloon is collapsed, the stent remains expanded, which helps keep the artery from narrowing or closing again.

The second major type of procedure, CABG, is used where the vessel narrowing or blockages are more extensive. CABG surgery creates new routes around narrowed and blocked arteries, allowing sufficient blood flow to deliver oxygen and nutrients to the heart muscle. Bypass grafting involves suturing graft vessels to the coronary arteries, bypassing the narrowing or blockage. CABG procedures are performed about 200,000 times per year in the U.S. and about 700,000 across the globe.

To perform a CABG procedure, the cardiac surgeon makes an incision down the middle of the chest and then saws through the breastbone (sternum) to be able to get to the heart. This procedure is called a median sternotomy. The heart is cooled with iced salt water, while a preservative solution is injected into the heart arteries. This process minimizes damage caused by reduced blood flow during surgery. Before bypass surgery can take place, a cardiopulmonary bypass must be established. Plastic tubes are placed in the right atrium to channel venous blood out of the body for passage through a heart-lung machine, which re-oxygenates the blood. The oxygenated blood is then returned to the body. The main aorta is clamped off during CABG surgery to maintain a bloodless field and to allow bypasses to be connected to the aorta. CABG surgery takes about four hours to complete. The aorta is clamped off for about 60 minutes and the body is supported by cardiopulmonary bypass for about 90 minutes.

The most commonly used vessel for the bypass graft is the saphenous vein from the leg, but chest wall arteries, particularly the left internal mammary artery, are also used. The major advantage of using internal mammary arteries is that they tend to remain open longer than venous grafts. Ten years after CABG surgery, only 66% of vein grafts are open compared to 90% of internal mammary arteries. However, artery grafts are of limited length, and can only be used to bypass diseases located near the beginning (proximal) of the coronary arteries.

An important unaddressed issue remains

While procedures for AMI are capable of restoring blood flow to the areas of the heart affected by the blockage, they do not address the restoration of the damaged tissue. While a certain portion of the heart tissue dies after AMI, a greater portion is in a state of stress. Following AMI, significant portions of this tissue may eventually die, leading to a significant loss of heart function. The result is a decrease in cardiovascular performance, which may eventually lead to heart failure. One in four patients develops heart failure within four years of AMI. This is a debilitating medical condition with very high medical and non-medical costs. In other patients, arrythmias may develop.

SmartPharm Therapeutics is developing treatments to ameliorate the damage caused by heart attacks on the cardiac tissue. These are designed to be used with the major procedures for treating AMI.

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