Welcome. My name is Jessica Ward,
and I'm a board-certified veterinary cardiologist and
assistant professor at the Iowa State University College of Veterinary Medicine.
Today, we'll be discussing basic concepts of the pathophysiology
and treatment of congestive heart failure in dogs and cats.
The first half of this lecture will introduce
concepts regarding pathophysiology of heart failure.
What is heart failure as a syndrome, how do we define it,
what are the hemodynamic determinants of cardiac output,
what are the clinical signs and syndromes associated with heart failure, and finally,
how do the body's neurohormonal compensatory systems respond to heart failure?
The goal of this pathophysiology review is to provide background
for understanding options for pharmacologic management of heart failure.
These two topics are inextricably linked.
We treat heart failure by giving medications that address
both hemodynamic and neurohormonal derangements.
Heart failure by definition is a clinical syndrome,
not a specific ideologic diagnosis,
wherein the heart cannot pump adequate volume of blood to both meet tissue demand for
oxygen and nutrient delivery while preventing
backup of blood and congestion or fluid accumulation.
Those are the jobs of the heart.
It's supposed to pump blood forward and meet the demands
of the body while preventing blood from backing up.
Heart failure occurs when the heart fails at one or both of those two jobs.
A key conceptual differentiation is between heart failure and hypovolemic shock.
In hypovolemic shock, the body is also unable to meet its tissue demands.
However, in hypovolemic shock it's because there's not
physically enough blood in the system for the heart to pump.
In contrast, in heart failure,
there's plenty of blood in the circulation.
In fact, sometimes there's too much intravascular volume.
The problem is that the heart is diseased and unable to handle that volume of blood.
Heart failure is not in and of itself a diagnosis.
It is a syndrome that occurs secondary to many different heart diseases.
Hypertrophic cardiomyopathy, dilated cardiomyopathy,
degenerative mitral valve disease,
patent ductus arteriosus, heart failure is
an end result of many different diseases such as any of these.
The term heart failure is thus more a marker of
disease severity rather than a description of any particular disease.
When using various staging systems such as
the ACVIM staging system or
the International Small Animal Cardiac Health Council staging system,
heart failure marks the onset of the more advanced stages of disease.