Light breaks where no sun shines
where no sea runs the waters of the heart
Push in their tides.
Many people feel that the great Welsh poet had been thinking about the complex and rather unique characteristics of the brain, and the heart while writing those lines. Though both the organs are equally important the heart does more manual work pumping millions of gallons of blood in a person’s lifetime. If a major defect develops in the heart the consequences are usually disastrous. Even when they experienced the well-known first symptoms of a heart attack—pain in the chest, difficulty in breathing, nausea and sweating—most people are reluctant to send for their family physician or go to the nearest hospital. They fear being ridiculed if the so-called attack should turn out to be mere indigestion or they fear that if it is indeed a regular heart attack they may be hospitalized for several seeks. So they choose to take a rather unwise and sometimes fatal decision to remain at home. If they seek prompt medical attention they could be helped.
Doctors, by using a procedure called ‘recanalisation’ now stop a heart attack before it does damage to the heart muscle. This new therapy first developed in Europe and now in wide-spread use even in the United States is based on the fact that a heart attack develops in stages. An attack often begins when a blood clot forms in a cholesterol laden coronary artery blocking the flow of blood to the heart muscle. The parts of the muscle that do not get oxygen die—a painful process that may go on for several hours eventually damaging the heart and often killing the victim. But if the clot is removed within six hours the muscle can be saved; after six hours the damage is irreversible.
In the earliest attempts at recanalisation doctors sent a wire enclosed in a plastic tube or catheter into the arm or leg artery of the patient and mapped its course on a fluoroscope as they guided it through a major blood vessel toward the heart. When the wire reached the heart they poked it through in an attempt to open the passage. There was of course the danger that pieces of clot might lodge elsewhere and cause problems. Use of the wire decreased after it ruptured a blood vessel in one patient (who later however recovered). Now recanalization is usually done without the wire. When the tube reaches the blood clot in a coronary artery, a drug streptokinase is injected dissolving the clot. The treatment takes two hours and most patients go home within two weeks. For the following few months they take blood thinning drugs to prevent formation of more clots. Patients susceptible to further heart attacks because of narrowed coronary arteries may require bypass surgery or angioplasty.
The record of recanalization is impressive if one considers the statistical data from many hospitals in the United States. Some doctors feel that since the procedure has to be done so early during a heart attack the sudden restoration of blood flow may worsen the injury to a heart muscle and disrupt the rhythm of the heart as research carried out on dogs has revealed. In any case doctors are generally against tubing which they feel can injure or block an artery. They also hold the view that even the most skillful surgeons may have difficulty in threading the tubing through blood vessels narrowed by arterial disease. Some doctors are of the opinion that recanalization is not desirable for all heart attack victims, as it would be too risky to administer blood-thinners (required after recanalization) to alcoholics, people with bleeding disorders and persons with blood pressure. Notwithstanding the above drawbacks many scientists feel that recanalization is better for many patients than no treatment at all. It opens up the artery and can save the heart muscle within the crucial six hour period—a fact that makes a difference in chances of survival of a patient.
There is another medical phenomenon known as ventricular fibrillation which takes 3,00,000 lives every year in the United States. The most common cause of fibrillation is an unsufficient supply of blood to the heart resulting in an electrical disorder that changes the regular heart beat into a useless flutter. Generally a victim of fibrillation outside the reach of a cardiac resucitation team is as good as dead. Now a new device known as the Automatic Implantable Defibrillator (AID) implanted inside a patient’s body delivers a massive life saving electrical punch (700 volts) to the heart at the right time.
The device was first tried on a patient in Johns Hopkins Hospital in Februrary 1980. Unlike the ordinary pace maker which gives out a low energy pulse to a sluggish heart, AID delivers a single shock one and a half million times as strong forcing the heart’s twitching muscle fibres to contract once again. The device produces as much energy as it would take to light fifty 100 Watt bulbs for a tiny fraction of second. This is less than a tenth of the amount of energy delivered by external paddles but has the same effect. This is because unlike the charge from the paddles, AID’s jolt is applied directly to the heart. AID is also ready to go to work instantly—a factor particularly relevant in an emergency. Its chest electrodes are connected by fine wires to a sensor and pulse generator of the size of a cigarette pack which is implanted under the skin of the abdomen.
The sensor monitors the heart continuously and when it detects fibrillation, it orders a surge of current from the power supply. If the first shock does not restore the heart beat AID can deliver three more at 15 second intervals. A persons who fails to respond to four’ shocks is obviously beyond even AID. Hence, there is no provision for a fifth jolt.
Some cardiologists feel that the device is of immense value to those who do not respond to available therapy, medical or surgical and to whom doctors have very little to offer, i.e. people likely to suffer from fatal heart attacks or are on the verge of death.
Commercial versions of AID are already in use. Their lithium batteries give them the potential of firing hundred times. Replacement of the batteries involves only minor surgery. Scientists were planning to equip AID with a cut off switch to be used if something goes wrong. No surgical procedure would be necessary to operate the switch. It can be flicked to the ‘off’ position by holding a powerful magnet over the patients abdomen.
The muscles of the human heart expand and contract millions of times a year without developing any fatigue. Yet deprivation of blood carrying oxygen even for a few minutes can cause irreparable damage to the heart. The development of techniques such as re-canalization and machines such as AID should be viewed as major advances in man’s efforts to protect this vital organ which is righty regarded as one of nature’s amazing marvels.
The situation has changed considerably since the inception of surgical coronary artery revascularization, and it continues to change as technological advances in the fields of cardiac surgery and cardiology occur. Research and development are needed in many areas of surgical revascularization, and new trials are needed to more fully delineate the benefits of on- and off-pump coronary revascularization, particularly with respect to the groups of patients who benefit from the off-pump approach. Robotic revascularization is still in its infancy, and better techniques and technologies need to be developed to serve patients who desire a minimally invasive approach. Hybrid revascularization is also still in its infancy, and rich opportunities are available going forward in developing this approach, both with respect to the “hard” technologies of procedural techniques involved and to the “soft” technologies of interdisciplinary cooperation between interventional cardiology and cardiac surgery teams. As these areas are developed, further outcomes data are needed to evaluate the efficacy and economic viability of the hybrid approach. With respect to the various arterial conduits possible for use in surgical revascularization the cardiac surgical world awaits with interest the 10-year data from the RAPCO(Radial Artery Patency and Clinical Outcomes) trial to better delineate the ultimate fate of the place of the radial artery graft in surgical revascularisation.