PATHOLOGIES OF CARDIOVASCULAR SYSTEM
The function of the cardiovascular system is to supply body cells and tissues with
oxygen-rich blood and eliminate carbon dioxide (CO2) and cellular wastes. Damage
and disease in the cardiovascular system greatly affect a person’s health and the
entire parts of his/her body. Cardiovascular diseases are conditions and diseases
that affect the heart and vasculature (blood vessels).
A good blood circulation requires the good cardiac output related to the capacity
of the heart to pump and the normal functionality of blood vessels that determine
the peripheral resistance. Blood pressure is the force exerted by the blood from
the heart against the walls of the blood vessels. It must be adequate to maintain
tissue perfusion during activity and rest. The maintenance of normal blood pressure
and tissue perfusion requires the integration of both systemic factors and local
peripheral vascular effects. Blood pressure is primarily a function of cardiac output
and systemic vascular resistance. Any condition that can have an impact on these
two aspects might have an impact on the blood pressure.
Hypotension is a decrease in systemic blood pressure below accepted values.
Even though there is no accepted standard hypotensive value, the blood pressure
less than systolic of 90-120mmHg/diastolic of 60-90mmHg is considered as
hypotension. The hypotension becomes a concern once pumping pressure is not
sufficient to perfuse key organs with oxygenated blood. This leads to symptoms
impacting the quality of life of a patient.
Causes and Pathophysiology
Blood pressure is determined by 2 major factors: cardiac output and total peripheral
vascular resistance. The cardiac output is determined by stroke volume and heart
rate. Therefore, any disease or pathology that impacts one or more of these factors
will induce hypotension.
Disease that reduces stroke volume or heart rate will decrease the total cardiac
output of the heart, therefore decreasing the ability to generate blood pressure.
Some medications including diuretics, calcium channel and beta blockers can
cause hypotension by having impact on stroke volume and heart rate.
A combination of the weakened autonomic nervous system and mild hypovolemia
from dehydration causes orthostatic hypotension. When lying flat, there is equal
and smooth distribution of fluid throughout the body. However, on standing the
heart rate fails to increase appropriately and peripheral resistance fails to increase
appropriately leading to a rapid, transient decrease in blood pressure that improves
with postural changes, then classic symptoms like dizziness and syncope occur.
Certain conditions can cause prolonged periods of hypotension that can become
dangerous if left untreated: pregnancy, due to an increase in demand for blood
from both mother and the growing fetus; large amounts of blood loss through injury; Medical Pathology, Student Book, Senior 526
impaired circulation caused by heart attacks or faulty heart valves, weakness and
a state of shock due to dehydration, anaphylactic shock due to a severe form
of allergic reaction, infections of the bloodstream, endocrine disorders such as
diabetes, adrenal insufficiency and thyroid disease. Nutrient deficiency like lack of
vitamin B12 and folate can cause low blood pressure due to reason that nutrients
are essential to produce the red blood cells and their deficiency can lead to drop in
blood pressure levels.
Hypotension as a result of troubles of the factors determining the blood pressure,
when persistent the patient might be into different types of shock:
Distributive shock occurs as a failure of the ability to maintain total peripheral
resistance with maintained cardiac function attempting to compensate. This is
associated with anaphylactic allergic reactions and septic shock.
Cardiogenic shock is a failure to achieve sufficient cardiac output with maintained
total peripheral resistance.
Hypovolemic shock is a loss of total blood volume such that a blood pressure is
not maintained. Both cardiac output and total peripheral vascular resistance are
maintained. This is possible due to trauma with massive loss of blood, overuse of
diuretic medications with fluid volume loss via urine, burns, diarrhea and vomiting,
hemorrhage, etc.
Obstructive shock occurs with the obstruction, constriction, or compression of the
cardiovascular system such that blood flow does not efficiently occur or there is a
decrease in stroke volume of the heart. This leads to drop in blood pressure.
Signs and symptoms
Patient with hypotension is most commonly asymptomatic. The chronic asymptomatic
hypotension isn’t usually harmful. But there are possibilities that sudden drop in
blood pressure may develop several health problems. The most common symptoms
are lightheadedness or dizziness. In extreme low blood pressures, syncope may
occur. Other symptoms are possible which typically begin from the underlying
etiology rather than hypotension itself. They may include chest pain, shortness of
breath, irregular heartbeat, headache, fatigue and weakness, pale skin color, rapid
breathing, blurred vision, fainting when having syncope, nausea, rapid pulse rate,
etc.
InvestigationsThe investigations to be requested depend on the suspected
cause. Basic lab work including complete blood count (CBC), cardiac enzymes,
renal function tests (urea and creatinine), liver function tests, blood smear for
malaria, blood sugar levels, electrolytes (sodium, potassium, chloride, calcium,
etc). If a patient present signs and symptoms of shock, all these investigations
must be ordered among others: chest x-ray, electrocardiogram, blood culture,
urine culture, ultrasound of the heart, chest computerized tomography scan with
angiography, etc).
Adequate Medical diagnosis
The diagnosis of hypotension requires relying on clinical manifestations supported
by laboratory and imaging investigations, and hemodynamic findings. Imaging or
hemodynamic indices of low cardiac output or systemic vascular resistance are not
diagnostic but may help to classify hypotension.
Treatment plan
Asymptomatic hypotension patient should not receive extreme interventions.
However, if symptoms are present, the treatment of hypotension should focus on
reversing the underlying etiology. The management must focus on:
• Patients should be assessed (monitoring of all vital signs) for possible need
for an immediate intervention so that lifesaving therapies can be administered
very early. After immediate stabilization, the comprehensive physical
examination must be followed.
• The airway should be stabilized and adequate intravenous access secured
so that patients can be immediately treated with intravenous fluids to restore
adequate tissue perfusion. The first priorities must be focused on the airway
and breathing with oxygen and/or mechanical ventilation, when necessary;
and insertion of intravenous catheter and IV fluids (Normal saline or Ringer
lactate) must be initiated to restore adequate tissue perfusion.
• Ensure the investigations needed are done to investigate the suspected
cause of hypotension
• Monitoring the inputs and outputs
• Treat underlying medical conditions, and this should include medications for
heart disease, diabetes, or infection. Patients with suspected infection (eg,
fever, hypotension, and a suspected septic source) must benefit from the
early administration of intravenous antibiotics.
• Shock-induced hypotension is the most serious form of the condition. Severe
hypotension must be treated immediately, should give IV fluids and possibly
blood products to increase the blood pressure and stabilize the vital signs and
hemodynamic status.
• Advise the patient to drink plenty of water to avoid hypotension due to
dehydration, especially if you are vomiting or have diarrhea. Staying hydrated
can also help treat and prevent the symptoms of mediated hypotension. If
you experience low blood pressure when standing for long periods, be sure
to take a break to sit down. And try to reduce your stress levels to avoid
emotional trauma.
• Treat orthostatic hypotension with slow, gradual movements. Instead of
standing up quickly, work your way into a sitting or standing position using Medical Pathology, Student Book, Senior 5 29
small movements. Avoid orthostatic hypotension by not crossing the legs
when you sit.
• Exercise regularly aiming at raising the heart rate and resistance exercises
two or three days a week.
Evolution and complications
The prognosis of hypotension is very good, but symptomatic hypotension might
have variable prognosis depending on the etiology and its severity.
Some complications resulting from Hypotension are:
• Shock depending on etiology of hypotension
• Injury resulting from falls due to fainting. Falls are particularly dangerous
because they cause other secondary injuries (fractures, lacerations, wounds,
limited movements, etc.) that might have an impact on a person’s quality of
life.
• Severe hypotension deprives the body of oxygen, which can damage the
heart, brain, kidney and other organs (multiple organ dysfunction); and this
condition can be life threatening if not immediately treated.