Surgical diseases of the heart

CARDIAC SURGICAL EMERGEN­CIES

Injuries of the heart fortunately are not com­mon. The heart is protected on all sides by the sturdy rib cage which affords protection from most blunt injuries to the chest. Penetrating wounds, such as from bullets and stabbing, may seriously injure the heart and great vessels. Large wounds may end rapidly in death by hemorrhage into the chest or externally. Smaller wounds may be less rapidly fatal; interference of the cardiac function may be by collection of blood in the pericardial sac, which restricts the heart movements, known as cardiac tamponade.

Early recognition and surgical correction are es­sential to save life. Operation entails approach to the heart by chest incision, evacuating the blood in the pericardial cavity, and repair of the heart wound. Urgent surgery often results in complete recovery. A great variety of other types of injuries of the heart and great vessels by penetrating objects may occur and many will be correctable by prompt operative interven­tion.

Cardiac arrest is the sudden cessation of the heart’s action. This may occur under several types of severe circulatory strain such as during major operation under general anesthesia. In this instance facilities are available for cardiac re­suscitation, or cardiac massage. As previously mentioned, the brain can tolerate a lack of oxy­gen for no longer than 3 minutes. If there is prompt recognition of cardiac arrest, immediate opening of the chest and massaging the heart by a squeezing motion will continue the circulation. The heart then resumes its normal pumping ac­tion. This emergency operation is augmented by artificial respiration and various drugs. After the heart has resumed its own automaticity, the chest is closed and the circulation continues nor­mally, often allowing completion of the primary operation. This is a dramatic and life-saving op­eration which rarely is necessitated but can be needed, so that all operating rooms are pre­pared for such.

HIGH BLOOD PRESSURE

Hypertension, or high blood pressure, is a disease affecting the heart and blood vessels. The main cause lies with the arteries. Blood pressure is controlled by the caliber of the smaller arteries, which may be influenced by several factors. The caliber of these vessels is controlled by the nerve supply to the muscle layer in the blood vessel walls. When the di­ameter of the vessels is made smaller, the pres­sure of the blood flow within the vessel is in­creased, and vice versa. Normally this is auto­matically controlled to increase the pressure and blood supply to regions of the body according to the oxygen needs with varying activity. In hypertension the arteries remain in constant con­striction, thereby increasing the blood pressure throughout the body. In another type the caliber of the arteries may be decreased by hardening of the arteries (arteriosclerosis) with ageing. With some kidney diseases a toxin may cause constriction of the arteries with subsequent hypertension. In some hormonal diseases, such as overactive thyroid, the blood pressure may be increased.

In prolonged hypertension the heart works much harder to force the blood through the con­stricted arterial tree. Like any other muscle used excessively, the heart muscle enlarges in attempts to supply the tissue demands for oxy­gen. As the heart enlarges, the valves may be stretched and not sufficiently close the cham­ber’s outlets; the murmur of valve insufficiency occurs. This further taxes the work of the heart.

Complications of hypertension include the so- called stroke wherein the pressure in a vessel in the skull becomes so great that the vessel ruptures and bleeds into and around the brain.

Treatment of hypertension is most often by medical measures and restricted activity. Drugs are used in attempts to increase the caliber of the spastic blood vessels; these may act on the vessels themselves or on the automatic nerves to the vessels. Some cases of high blood pressure

may be benefited by surgical treatment, which is directed at disrupting the nerve supply to the spastic arteries. The vessels are then no longer constricted and the pressure returns to normal.