Hypertension Blog

Hypertension is a major modifiable risk factor for CAD. Normally, CAD takes years to develop, but hypertension accelerates the atherosclerotic process that causes CAD. Then, as CAD progresses, the resulting arterial narrowing worsens the hypertension.

Its Pathophysiology

In CAD, atherosclerotic plaques collect in the arteries. These deposits, which line the intimal layer, consist of cholesterol and lipids.

In a person with hypertension, the elevated blood pressure causes high shear stress, speeding the atherosclerotic process. As a result, the artery’s endothelial lining is injured. Then, platelets begin to accumulate at the site of the damage, resulting in a denuding injury.

Alternatively, hypertension can result when CAD causes a non denuding injury. After the endothelium is damaged, low-density lipoproteins (LDLs) and growth factor from platelets stimulate smooth-muscle proliferation and arterial-wall thickening. Smooth-muscle cells proliferate, trapping lipids. Over time, the lipids calcify and irritate the endothelium, causing platelets to adhere and aggregate. Thrombin is generated, and fibrin and thrombi form.

With denuding and nondenuding injuries, the thickened walls of atherosclerotic arteries lose their elasticity. Thus, the heart must beat harder to pump blood through the restricted vessels, increasing blood pressure even more .

Treating a patient with CAD involves risk-factor management, drug therapy, and, if needed, invasive procedures or surgery. Treatment has two goals -

• Reducing myocardial oxygen demand
• Increasing oxygen supply.

Invasive Procedures and Surgery

In severe cases of CAD, a patient may require an invasive procedure to relieve the signs and symptoms of the disease. Several procedures use a balloon-tip coronary artery catheter to restore blood flow to blocked coronary arteries by enlarging the arterial lumen.

The most common of these procedures is percutaneous trans luminal coronary angioplasty, which uses balloon inflation to clear arteries. Other procedures include intra-coronary stenting, atherectomy, and laser angioplasty.

A physician performs these procedures in a cardiac catheterization laboratory using coronary angiography to evaluate progress. He inserts a femoral artery sheath and threads a catheter with a balloon, rotor blade, or laser tip through the aorta into the affected coronary vessel.

When the procedure is complete, the physician removes the catheter but leaves the sheath in place for up to 8 hours. Most patients receive a heparin infusion during the procedure and for several hours afterward. Some require long-term anticoagulant therapy.

If the procedure fails to remove the blockage, the patient usually will need coronary artery by­pass grafting. This surgery involves bypassing the occluded artery with a graft from a saphenous vein or internal mammary artery. The graft is sutured to the aorta and anastomosed to the affected coronary artery.

Coronary Artery Bypass Grafting

If your patient is scheduled for coronary artery bypass grafting, thoroughly assess his cardiovascular status before the operation.

After the procedure, monitor your patient’s hemodynamic status. Maintain the patency of his chest tube (or tubes) and assess tube drainage. Also, observe the surgical wound for signs and symptoms of infection and provide routine wound care as necessary.

Monitor the patient’s fluid balance and serum electrolyte levels. Administer fluids, blood products, or vasoactive infusions, as ordered. Record his fluid intake and output and daily weights.

Monitor the patient’s breath sounds and chest X-ray results for signs of atelectasis. Help him increase his activity level gradually, following the guidelines of his cardiac rehabilitation program.

Coronary Artery Catheterization

lf your patient is scheduled for coronary artery catheterization, explain the procedure to him and answer any questions. Tell him that he’ll be awake during the procedure and that he may be asked to assist with catheter placement by taking deep breaths.

After the procedure, your patient’s arterial and venous sheaths may remain in place for up to 8 hours, if he has received a thrombolytic drug. Connect the sheaths to a heparin flush setup to maintain patency. Ask the patient about back pain, a possible indication of retroperitoneal bleeding from the sheath site. And frequently check the insertion site for signs of bleeding.

Instruct your patient to keep the affected leg straight and to stay in bed with the head of the bed at a 45-degree angle or less.

After the sheaths have been removed and hemostasis has been achieved, a pressure dressing will be applied. Frequently assess the circulation of the affected leg by checking its warmth, color, and distal pulses. Watch your patient for signs and symptoms of complications, such as chest pain, shortness of breath, and changes in mental status. Monitor his heart rate and rhythm carefully. Also, monitor him for angina, which could be caused by coronary vasospasm or reocclusion. Report any unusual findings to the physician.

If you’re administering a thrombolytic drug, monitor your patient’s heart rhythm for reperfusion arrhythmias. Also, monitor him for reocclusion of the coronary artery. Report any chest pain or ischemic changes on the ECG to the physician. To reduce the risk of reocclusion, begin heparin therapy after thrombolytic therapy, as prescribed, and monitor your patient’s partial thromboplastin time (PTT). Titrate the heparin to maintain the PTT at twice the control time.Assess the puncture site for bleeding and hematoma formation. Also, avoid performing venipunctures or a phlebotomy after injecting the thrombolytic drug. Assess the patient’s pedal pulses distal to the puncture and immediately report any loss of pulse. Monitor his vital signs for signs of hemorrhage, such as hypotension and tachycardia. If you’re administering streptokinase, observe the patient for an allergic reaction.

Some More Facts

Help your patient identify his personal risk factors for CAD and develop a realistic risk-reduction plan. Encourage him to enroll in a cardiac rehabilitation program for exercise training to improve his cardiovascular endurance.

Depending on the severity of the patient’s disease, tell him that he may need to exercise while attached to an ECG monitor to increase his confidence and allow detection of ischemia and arrhythmias. Tell him that as he progresses, he’ll be instructed about home activities that he can perform safely. And explain that cardiac rehabilitation professionals will help determine when he can return to work and resume recreational activities.

A cardiac rehabilitation program also may have classes in which he can learn about the anatomy and physiology of the heart and the pathophysiology of CAD. The program may help him by offering psychosocial support as he makes lifestyle changes to manage his disease.

If your patient is scheduled for an invasive procedure, explain the procedure, the expected outcome, and the care he’ll receive afterward. If a surgical procedure will involve a saphenous vein graft, make sure he understands that the physician will make an incision in his leg.

Before he’s discharged, instruct your patient and his family about prescription drugs he must take at home. Make sure they know the proper administration route, whether oral, trans dermal, or sublingual. In particular, ensure that the patient knows how to use sublingual nitroglycerin for angina. Discuss the therapeutic and adverse effects of each drug. Also, teach him the symptoms that warrant an immediate call to his physician.

Risk Factors

To slow the progression of CAD, a patient needs to change his lifestyle. Be sure you teach your patient the importance of taking the following measures:

• quitting smoking
• controlling his weight
• controlling his lipid levels
• reducing stress
• lowering his elevated blood pressure
• exercising.