Cardiovascular PART 1

Physiologic Process of Perfusion

The process of delivering oxygenated blood and nutrients to tissues and removing waste products. It relies on an efficient cardiac pump, intact vascular system, and adequate blood volume.

Conductive System:

Specialized cells initiate and transmit electrical impulses, leading to myocardial contraction.

Conductive System: SA Node (Sinoatrial Node)

Intrinsic pacemaker, initiates electrical impulse.

Conductive System: AV Node (Atrioventricular Node)

Delays impulse to allow ventricular filling.

Conductive System: Bundle of His (AV Bundle)

Transmits impulse from AV node to ventricles

Conductive System: Purkinje Fibers

Rapidly distribute impulse throughout ventricles, causing contraction.

Cardiac Cycle:

Rhythmic pumping of the heart, involving systole (contraction/emptying) and diastole (relaxation/filling).

Cardiac Cycle: Diastole

Ventricles relax and fill with blood. Atria contract (atrial kick) to push the last 25% of blood into ventricles.

Cardiac Cycle: Systole

Ventricles contract and eject blood

Electrocardiogram (ECG/EKG) Waves: P Wave

Atrial depolarization (atrial contraction).

Electrocardiogram (ECG/EKG) Waves: QRS Complex

Ventricular depolarization (ventricular contraction); atrial repolarization is hidden within this complex

Electrocardiogram (ECG/EKG) Waves: T Wave

Ventricular repolarization (ventricular relaxation).

Preload

Volume of blood in ventricles at the end of diastole (end-diastolic volume), reflecting the stretch of ventricular muscle fibers. Increased preload leads to increased stroke volume (up to a point).

Afterload

Resistance the left ventricle must overcome to eject blood into the aorta. Influenced by systemic vascular resistance and aortic pressure. Increased afterload decreases stroke volume.

Factors Influencing Blood Pressure (BP)- Cardiac Output (CO):

Volume of blood pumped by the heart per minute (CO = HR x SV). Increased CO increases BP.

Factors Influencing Blood Pressure (BP)- Peripheral Vascular Resistance (PVR)

Resistance to blood flow in the systemic circulation. Increased PVR increases BP.

Factors Influencing Blood Pressure (BP)- Peripheral Vascular Resistance (PVR)- Blood Vessel Diameter:

Vasoconstriction (narrowing) increases PVR; vasodilation (widening) decreases PVR.

Factors Influencing Blood Pressure (BP)- Peripheral Vascular Resistance (PVR) Blood Viscosity

Thicker blood (higher viscosity) increases PVR.

Factors Influencing Blood Pressure (BP)- Peripheral Vascular Resistance (PVR)- Total Vessel Length:

Longer vessels increase PVR.

Factors Influencing Blood Pressure (BP) Volume of Circulating Blood:

Increased blood volume increases BP.

Factors Influencing Blood Pressure (BP) Elasticity of Blood Vessels:

Stiff, less elastic vessels (e.g., arteriosclerosis) increase BP as they cannot absorb pressure changes as effectively.

Blood Pressure Regulation (Short term) Baroreceptors

Pressure-sensitive receptors in carotid arteries and aortic arch. Detect changes in BP and send signals to brainstem.

Blood Pressure Regulation (Short term)- Parasympathetic Fibers (Vagus Nerve):

Decrease heart rate and contractility, leading to decreased CO and BP.

Blood Pressure Regulation (Short term)- Sympathetic Response (Adrenergic System):

Increases heart rate, contractility, and vasoconstriction, leading to increased CO, PVR, and BP.

Blood Pressure Regulation (Long term)- Renin-Angiotensin-Aldosterone System (RAAS)

Kidneys release renin in response to low BP. Renin converts angiotensinogen to angiotensin I, then to angiotensin II (a potent vasoconstrictor). Angiotensin II stimulates aldosterone release, leading to sodium and water retention, increasing blood volume and BP.

Blood Pressure Regulation (Long term) Anti-Diuretic Hormone (ADH) / Vasopressin:

Released by posterior pituitary in response to increased plasma osmolality or decreased blood volume. Causes water reabsorption in kidneys and vasoconstriction, increasing blood volume and BP.

Pathophysiology of Hypertension (HTN)

BLANK results from sustained elevation of systemic arterial pressure. It often involves a combination of increased CO (due to increased blood volume or heart rate/contractility) and/or increased PVR (due to vasoconstriction, increased blood viscosity, or decreased vessel elasticity). Long-term dysregulation of short-term and long-term BP control mechanisms contributes to its development.

Hypertensive grading

Hypertensive grading

Hypertensive Grading

• Grade 1 (Stage 1): Systolic 130-139 mmHg OR Diastolic 80-89 mmHg.

• Grade 2 (Stage 2): Systolic ≥140 mmHg OR Diastolic ≥90 mmHg.

• Grade 3 (Hypertensive Crisis): Systolic ≥180 mmHg AND/OR Diastolic ≥120 mmHg (requires immediate medical attention).

Risk Factors for Hypertension

• Modifiable: Smoking, obesity, physical inactivity, high sodium intake, excessive alcohol consumption, stress, diabetes mellitus, dyslipidemia.

• Non-modifiable: Age, family history, race (e.g., African Americans have higher incidence and severity), genetics.

Subjective Data: Cardiovascular Assessment Components MEMORIZE

• Chest Pain: Onset, location, character (burning, aching, cramping, stabbing), radiation, aggravating/alleviating factors, associated symptoms (dyspnea, diaphoresis).

• Dyspnea: Shortness of breath, activity level that triggers it, onset, duration, positional effects (orthopnea), paroxysmal nocturnal dyspnea (PND).

• Cough: Duration, character, associated symptoms.

• Fatigue: Onset (sudden/gradual), timing (morning/evening), impact on ADLs.

• Cyanosis/Pallor: Bluish discoloration (cyanosis) or paleness (pallor) of skin/mucous membranes.

• Edema: Swelling in extremities, onset, timing (worse at end of day), unilateral/bilateral, associated symptoms (pain, heat, redness).

• Nocturia: Urination at night, frequency, recent changes.

• Past Cardiac History: Previous heart disease, surgeries, diagnostic tests.

• Family Cardiac History: HTN, CAD, diabetes, obesity, sudden death at young age.

• Patient-Centered Care: Nutrition, smoking, alcohol, exercise, drug use.

Nocturia

Urination at night, frequency, recent changes.

Dyspnea

Shortness of breath

Edema

Swelling in extremities, onset, timing (worse at end of day), unilateral/bilateral, associated symptoms (pain, heat, redness).