Key Topics

• • Cardiovascular physiology & pathology
• • Drugs used in cardiovascular disease
• • Cardiovascular medications of relevance to the practice of dentistry

Learning Objectives

• • To be able to identify the key components of the cardiovascular system
• • To be able to list the main cardiovascular diseases
• • To be able to list the different classes of cardiovascular medications
• • To be able to identify the medications of relevance to the practice of dentistry and identify the reasons why these medications are of importance to dentistry

Introduction

Patients with cardiovascular diseases commonly attend for dental treatment. Such patients are often prescribed multiple medications to manage their conditions, several of which have potentially serious implications in the practice of dentistry. Therefore, it follows that dental practitioners should have an up-to-date working knowledge of currently prescribed cardiovascular drugs, coupled with a thorough understanding of how these drugs may impact on the practice of dentistry.

This chapter will briefly consider the important aspects of cardiovascular physiology and pathology before discussing the drugs used in the management of cardiovascular disease. Finally, the effects of cardiovascular medications of relevance to the practice of dentistry will be considered.

Cardiovascular physiology

The cardiovascular system is a collection of organs that function together (organ system), thus permitting blood to circulate and transport: nutrients (such as glucose, amino acids and electrolytes), oxygen, carbon dioxide, hormones and blood cells, to and from the cells of the body. Moreover, the cardiovascular system also: stabilizes temperature and pH, facilitates the body’s immune system and maintains homeostasis.

Blood is a fluid consisting of cellular components suspended within a plasma matrix. Blood plasma is the pale yellow liquid component of blood which makes up around 55% of the total blood volume. Plasma comprises mainly of water (up to 95% by volume), in addition to 6–8% dissolved proteins (e.g. serum albumins, globulins, and fibrinogen), glucose, clotting factors, electrolytes (e.g. sodium, calcium, magnesium, chloride and bicarbonate), hormones and carbon dioxide. Plasma plays the role of the chief medium for waste product transportation in the body. The cellular component of blood comprises mainly of red blood cells, white blood cells and platelets.

The main components of the human cardiovascular system (CVS) are the heart, blood and blood vessels. In simple terms, the CVS is considered to be a ‘closed’ system (blood never leaves the network of arteries, veins and capillaries), which comprises of the pulmonary circulation (‘loop’ through the lungs allowing oxygenation of the blood) and the systemic circulation (‘loop’ through the rest of the body to deliver oxygen). The heart pumps oxygenated blood to the body and deoxygenated blood to the lungs (see Figure 18.1). The coronary circulation provides the blood supply to the cardiac muscles – originating near the root of the aorta from two arteries: the right and left coronary arteries. The majority of cardiac perfusion occurs during diastole (relaxation of heart muscle); with blood then returning through the coronary veins into the right atrium.

The circulation allows oxygen and nutrients to diffuse from the blood vessels and enter interstitial fluid, which carries oxygen and nutrients to the target cells, with carbon dioxide and waste products travelling in the opposite direction.

Cardiovascular pathology

Cardiovascular diseases involve the heart or blood vessels and include: ischaemic heart disease (IHD), stroke, hypertension, cardiac arrhythmias, venous thromboembolism and peripheral vascular disease (PVD). Cardiovascular diseases are the leading cause of death globally, and tend to become more prevalent with increasing age. The most common cause of cardiovascular disease is atherosclerosis, which is the occlusion and thickening of the systemic arterial vessels due to a chronic inflammatory response. Predisposing factors for atherosclerosis formation include: tobacco smoking, hypertension, hypercholesterolaemia, excessive alcohol consumption, obesity and diabetes mellitus. Atherosclerosis is the underlying mechanism in IHD, PVD and many strokes.

Hypertension

Hypertension is a chronic condition characterized by raised arterial blood pressure. Blood pressure is expressed as two measurements – the systolic and diastolic pressures. The systolic pressure is the maximum pressure of the arterial system – which occurs during systole (contraction of the cardiac muscles). Conversely, the diastolic pressure is the minimum arterial pressure, which occurs during diastole (relaxation of the cardiac muscles). Blood pressure is represented as the systolic pressure over the diastolic pressure, for example 120/80. Normal blood pressure at rest is within the range of 100–140 millimetres of mercury (mmHg) for systolic and 60–90 mmHg for diastolic. In adults, hypertension is present when blood pressure measured at rest is persistently at or above 140/90 mmHg.

Hypertension is often asymptomatic and is usually identified by the screening of blood pressure by healthcare professionals, or by patients using electronic blood pressure monitors at home. Sustained hypertension over a prolonged period is a major risk factor for hypertensive heart disease (e.g. left ventricular hypertrophy, cardiac failure), coronary artery disease, stroke, aortic aneurysm, chronic kidney disease and peripheral arterial disease.

Hypertension is classified as either essential (primary) hypertension or secondary hypertension. Most cases of hypertension (90–95%) are classed as primary hypertension; defined as high blood pressure with no obvious underlying cause. The remaining 5–10% of cases are considered to be secondary hypertension; hypertension due to an identifiable pathology, for example chronic kidney disease, excess aldosterone production (e.g. Conn’s syndrome) or excess catecholamine production (e.g. pheochromocytoma).

Cardiac failure

Cardiac failure occurs when the heart is no longer able to function sufficiently well enough to maintain the blood flow requirements of the body. The common causes of cardiac failure include coronary artery disease, previous myocardial infarction, hypertension and valvular heart disease. Cardiac failure is loosely categorized into left-sided heart failure (reduced ability of left ventricle to send blood to peripheral circulation) and right-sided heart failure (reduced ability to send blood to the lungs). Biventricular failure (i.e. both sides of the heart) is fairly common, and often failure of one side of the heart will lead to failure of the other side.

Cardiac arrhythmia

Cardiac arrhythmias are a group of conditions in which the cardiac rhythm is irregular, too fast, or too slow. Cardiac arrhythmias can be identified by feeling a patient’s pulse, or from an electrocardiogram (ECG). In an adult, a cardiac rhythm at rest that is too fast (above 100 beats per minute) is called tachycardia; and a heartbeat that is too slow (below 60 beats per minute) is called a bradycardia. Many arrhythmias are not particularly serious, although some predispose a person to complications such as heart failure, stroke or on occasions cardiac arrest and death.

Venous thromboembolism

Venous thromboembolism comprises of deep vein thrombosis (DVT) and pulmonary embolism. DVT is the formation of a blood clot (thrombus) within a deep vein, predominantly in the legs. Pulmonary embolism, is a potentially life-threatening complication caused by the detachment (embolization) of a thrombus which travels to the lungs and becomes lodged in the pulmonary arterial supply.

The three principle factors which contribute to the development of deep vein thromboses comprise Virchow’s triad — venous stasis, hypercoagulability or changes in the endothelial blood vessel lining. Hypercoagulability can be congenital (e.g. Factor V Leiden thrombophilia, Antithrombin III deficiency) or acquired (e.g. anti-phospholipid syndrome, polycythaemia vera).

Peripheral vascular disease

Peripheral vascular disease (PVD), also known as peripheral artery disease, is the pathological occlusion of the arteries that don’t supply the brain or the heart. Morbities associated with PVD include: skin ulceration, infection, tissue necrosis or limb amputation. The primary mechanism for narrowing of the peripheral arteries is atherosclerosis – the main risk factor being cigarette smoking, in association with other factors such as diabetes mellitus, hypertension and hypercholesterolaemia. Not surprisingly, PVD is often co-morbid with ischaemic heart disease and stroke, due in large part to the common risk factors shared between the conditions.

Stroke

Stroke, previously known also as cerebrovascular accident (CVA) is characterized by impaired cerebral perfusion, leading to infarction and death of brain tissue. There are primarily two main types of stroke: the most common being ischaemic (due to lack of adequate blood flow), followed by haemorrhagic (due to an intracranial bleed). Hypertension is the most significant risk factor for stroke, followed by other cardiovascular disease risk factors, for example cigarette smoking, hypercholesterolaemia, diabetes mellitus, atrial fibrillation (cardiac arrhythmia) and anticoagulant medications. The morbidity of stroke is very variable and can range from negligible permanent neurological deficit to permanent muscle weakness, paralysis and death.

Drugs used in cardiovascular disease

The Drugs used in cardiovascular disease will now be discussed in turn. These are listed in Table 18.1.