Cardiovascular System & Blood Pressure

• Cardiovascular aging is a significant risk factor for cardiovascular disease.

Cardiovascular System Anatomy

• Consists of interior heart, superior vena cava, aorta, pulmonary artery, left and right atrium, left and right ventricle.
• The heart wall sections are the outer pericardium, muscle layer and inner lining.

Endothelium

• Endothelium in vessels is composed of smooth muscle and connective/elastic tissue.

Myocardial Function

• Diastolic aspects involve blood volume and venous tone, which affects preload.
• Systolic elements are heart rate, contractility, and peripheral resistance affecting afterload.
• Myocardial O2 Requirement is involved in delivering O2, transporting nutrients, removing waste, protecting the body, and regulating pH, water/ions, and body temperature.

Blood Pressure Regulation

• Regulation includes the vasomotor center, veins, heart, arterioles, and kidney.
• Regulation also includes sympathetic nerve terminals, aldosterone, angiotensinogen, ACE, renin, angiotensin II, and angiotensin I.

The Framingham Heart Study

• Approximately 75 years ago, Framingham was selected as the study site.
• 5,209 healthy residents between 30 and 60 years of age were enrolled as the first cohort, making it the first major cardiovascular study to include women.
• In 1971, 5,124 children and their spouses from the original cohort were recruited for the "Offspring Study."
• In 2002, 4,095 participants were included in the "Third Generation" cohort.

Cardiovascular Disease Risk Factors

• Studying multiple predictors contributing to cardiovascular disease led to developing risk calculators.

Aging and the Vasculature

• Changes in endothelial cell shape and size decreases function.
• Major arteries increase thickness of smooth muscle and elastic layers, leading to stiffening and elevated systolic pressure.
• Contributors to stiffening arteries includes the accumulation of cellular debris, disintegration of the elastic membrane, and increased cross-linked collagen.
• Capillaries increases wall thickness and causes a decline in number and density.

Endothelial NAD+-H2S Signaling Network

• Impairment of Endothelial NAD+-H2S Signaling Network is a Reversible Cause of Vascular Aging.
• The study was conducted by Das et al 2018, and the experiments were done on mice.

Aging and the Heart

• Structural changes in the aging heart include enlarged left atrium and/or ventricle, increased size and decreased number of myocytes.
• Includes left ventricular wall thickening, thickening or degenerating heart valves, and lipofuscin deposits.
• Individuals with kidney or liver damage may experience more dramatic changes.

Functional Changes with Aging

• There is a slight increase in resting systolic blood pressure.
• Maximal heart rate and oxygen uptake decreases during stress or exercise, reducing workload.
• Additional changes include decreased norepinephrine levels in heart, beta-receptor sensitivity, prolonged relaxation phase, and response to renin-angiotensin-aldosterone system.
• Further changes includes decreased blood volume, red blood cells, and baroreceptor sensitivity.
• Alterations leads to a decreased blood flow to organs and tissues.

Heart and Stroke Foundation Report

• The face of heart disease in Canada has changed to include previously immune groups.
• Between 1994 and 2005, rates of high blood pressure among Canadians skyrocketed by 77%, diabetes by 45%, and obesity by 18%, all major risk factors for heart disease.

Future Predictions

• Within the next 25 years, deaths from heart disease and stroke will increase seven times faster than Canada's population, as most baby boomers will be in their 70s.
• Hospitalizations from heart disease and stroke will increase three times faster than the population over the next 45 years.

Hypertension

• Hypertension is the most common cardiovascular disease.
• Arteries progressively stiffen with age due to genetics, stress, high salt intake, smoking, lack of aerobic exercise, hypercholesterolemia, and diabetes.
• 23% of Canadians have hypertension, and require treatment.
• Untreated hypertension causes damage to blood vessels, renal failure, coronary disease, and stroke.
• Treatment slows blood vessel damage and decreases morbidity and mortality.

Blood Pressure Threshold for Hypertension Treatment

• Diastolic or systolic hypertension: ≥140/90 mmHg
• Isolated systolic hypertension: ≥160 mmHg
• Diabetes: ≥130/80 mmHg
• Renal disease: ≥130/80 mmHg

Hypotension

• Defined as systolic/diastolic blood pressure ≤ 90/60 mmHg.
• Common symptoms: dizziness, confusion, lethargy, and fainting spells.
• Common causes: medical/surgical conditions, hormonal imbalances, dehydration, and medication (anti-hypertensives).
• Types of hypotension: orthostatic, post-prandial, and vasovagal syncope.

Hypotension in the elderly

• Leads to falls and injury.
• A 2010 study in Leuven, Belgium, found orthostatic hypotension predicts subsequent cardiovascular events.
• Systolic drop of 20 mmHg or more.
• Treatment involves modifying activity, replacing lost fluid/blood, adjusting medication, increasing salt intake, vasopressors, and compression stockings.

Angina Pectoris

• Coronary blood vessels supply the heart with O2 and nutrients.
• Local blood flow is regulated by the heart's needs (O2 demand).
• Insufficient coronary blood flow leads to O2 deprivation, decreasing muscle strength and causing acute heart failure
• O2 deprivation equates to muscle pain
• The term "pectoris" refers to the thorax.
• Angina pectoris leads to chest pain.
• This is caused by an imbalance between O2 supply and demand.

Heart Failure

• Occurs when the delivery of blood/cardiac output is inadequate for the O2 and nutritional needs of the body.

Aneurysms

• Involves enlargement of a blood vessel (usually an artery) due to weakening of the vessel wall, collagen and elastin breakdown, atherosclerosis, trauma and infection.
• Rupture can be fatal.
• It occurs most commonly in males over 60 years of age.
• Risk factors include diabetes, obesity, hypertension, tobacco use, alcoholism, high cholesterol, copper deficiency, increasing age, and syphilis infection.

Normal Cardiac Rhythm

• Involves the SA node, AV node, and Purkinje fibers.
• Normal heart rate is 60-80 beats per minute.

Arrhythmias

• Atrial arrhythmias don't always lead to ventricular arrhythmias and might not affect cardiac output.
• Atrial flutters include 200-350 beats per minute.
• Atrial fibrillation includes 300-500 beats per minute and can be irregular and disorganized.
• Ventricular fibrillation leads to irregular rapid contraction of ventricles, which causes it to not pump blood properly.
• Untreated ventricular fibrillation is fatal.
• Additional age-related risk factors for arrhythmias includes vascular stiffness, decreased beta-receptor response, valve degeneration, cumulative effects of lifestyle choices, medication, other diseases, and disorders.