5. Heart failure (clinical aspects, medical therapy, emergency treatment of cardiac diseases) Flashcards
Clinical aspects?
Clinical Aspects
Where the cardiac output (performance) can’t deliver the necessary
amount of blood to the tissues
Primary heart disease → Secondary cardiac changes
Heart disease ≠ Circulatory failure
Aetiology?
AETIOLOGY
Inadequate/↓Cardiac output → ↑ Blood volume within the
cardiovascular system → Congestion → Fluid accumulation in the
tissues = Oedema
Cardiac output (CO) = Heart Rate × Stroke Volume
The stroke volume is composed of:
§ Preload
§ Afterload
§ Contractility
Preload
Initial stretching of the cardiac myocytes → Left ventricular enddiastolic volume
↑ Preload → ↑ CO → Congestion; Oxygen demand
Afterload
The load which the heart must pump against → Determined by
vascular resistance
↑ Afterload → ↓ CO → Hypertrophy & ↑ Oxygen demand
Contractility
The ability of the heart to contract (affected by arrhythmias)
↑ Contractility → ↑ CO → ↑ Oxygen & energy demand
Generally, arrhythmias ↓ CO
Heart rate
↑ Contractility → ↑ CO → Ultimately ↓ CO though
Distensibility
Ability of the heart to be stretched
↑ Distensibility → ↑ CO → Pathological dilation; ↑ Oxygen &
energy demand
Rhythm
Synchronisation of heart beat
Compensation of heart failure>
COMPENSATION OF HEART FAILURE
The body will compensate the heart failure by prioritising:
§ Arterial blood pressure in the brain, heart & kidneys
§ Arterial blood pressure in other organs
§ Venous blood pressure (preload) by keeping at a
reasonably low level
Neurohormonal compensatory processes
To keep blood volume, stroke volume & arterial pressure optimal
This is completed by:
§ ↑ Heart rate (chronotropic effect)
§ ↑ Myocardial activity (inotropic effect)
§ Peripheral vasoconstriction
§ ↑ Blood volume (RAAS system)
Neural compensatory processes
↓ BP → ↑ Sympathetic tone
This leads to:
§ + Inotropic, lusitropic (relaxation), chronotropic effects
§ Vasoconstriction
§ Arrhythmias
§ ↑ Renin synthesis
§ ↓ Parasympathetic tone
Chronic sympathetic activation → ↓ Baroreceptor sensitivity
↓ β-receptor density & sensitivity
Renin-Angiotensin-Aldosterone System (RAAS)
Effects:
§ Haematogenous metastasis § GI Diseases
§ Pulmonary embolism § CT Diseases
§ FIP
§ Trauma § Ruptured granuloma
§ Neoplasia § Thymus apoplexy (dog)
§ Coagulopathies
Cardiac output (CO) = Heart Rate × Stroke Volume
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§ Na + H2O retention; K excretion
§ Vasoconstriction
§ ↑ Sympathetic tone
§ Myocardial fibrosis, necrosis & hypertrophy
§ Cardiac remodelling → Left ventricular hypertrophy
§ Arrhythmias
These neurohormonal effects ↑ afterload → ↑ Myocardial oxygen
consumption
Progression of cardiac failure?
PROGRESSION OF CARDIAC FAILURE
Myocardial damage; ↑ Congestion
§ RAAS becomes permanently activated
§ ↑ Heart rate
§ Insufficient oxygen & energy supply of cardiomyocytes
§ Endothelin release → Vasoconstriction; Myocardial
hypertrophy
Inflammation as a result of heart failure?
INFLAMMATION AS A RESULT OF HEART FAILURE
Heart failure → ↑ In inflammatory mediators → Myocardial fibrosis;
Necrosis; Apoptosis
Inflammatory mediators:
§ Paracrine molecules § TNF-ɑ
§ Interleukins
Effects of the inflammatory mediators:
§ Cardiac cachexia
§ ↓ Myocardium contractility
§ Myocardial hypertrophy; Fibrosis
§ iNO (free radical) synthesis
Effects of the free radicals:
§ ↓ Contractility
§ Myocardial cell death; Apoptosis
Cardiac remodelling?
CARDIAC REMODELLING
Causes: Autonomic nervous system; RAAS; Inflammatory mediators
Macroscopic remodelling: Shape & size of the heart
Microscopic remodelling: Necrosis; Apoptosis; Fibrous tissue;
Cellular uncoupling
Leads to functional & electrophysiological changes → Impaired
contractility → Arrhythmias
Classification of heart failure left and right sided heart failure?
CLASSIFICATIONS OF HEART FAILURE
§ By Course: Acute/Chronic
§ By Demand: Absolute; Relative
§ By Anatomy: Left-sided; Right-sided
§ By Function: Systolic; Diastolic
§ By Direction: Forward; Backward
§ By Grade: Compensatory; Decompensatory
LEFT-SIDED HEART FAILURE - PATHOLOGY
Pathological lesions: Pulmonary oedema (dogs & cats); Pleural fluid
accumulation (cats): Modified transudate (proteinaceous & chylous)
CSx: Tachypnoea; Cough; Adam-Stokes syndrome (due to cerebral
hypoxia); Mild prerenal azotaemia
RIGHT-SIDED HEART FAILURE - PATHOLOGY
Pathological lesions: Pleural & pericardial fluid accumulation
(modified transudate); Congestion in the abdominal organs
CSx: Ascites (dogs & cats); Congested jugular veins; Positive
Cause of heart failure and medical therapy?
CSx of Heart Failure
See above for specific CSx of LSHF & RSHF
Pale/cyanotic mucosa; Prolonged CRT
Fatigue; Weakness; Exercise intolerance; Weight loss; Cachexia
Tachycardia; Lack of respiratory arrhythmia
Medical therapy
Therapy can vary from conservative therapy, surgery to
catheterisation
Overall: Treat the cause; Relieve symptoms; Stop/slow progression
This is done by:
§ ↓ Preload § ↑ Contractility
§ ↓ Afterload § Treat any arrhythmias
§ Treatment of neurohormonal overcompensation
↓ PRELOAD
Medication: Diuretics; Vasodilators; Pimobendan
Diuretics:
Loop diuretics: Furosemide & Torsemide
§ Given in cases of pulmonary oedema;
ARDS
§ Activates RAAS
§ Antitussive, Anti-inflammatory &
bronchodilation effects
Thiazides: Chlorothiazide; Hypothiazide
K-sparing diuretics: Amiloride; Triamterene
↓ AFTERLOAD
Arterial dilators: Amlodipine; Hydralazine (these cause
hypotension)
Pimobendan
↑ CONTRACTILITY
Calcium sensitisers: Pimobendan (CardisureⓇ )
§ ↑ Relaxation; Vasodilator; Venodilator
§ Used in congestive heart failure
Digoxin: Mild inotrope;↓Heart rate & adrenergic overload;
Maintains baroreceptor function
Beta-adrenergic stimulation (acute cases only)
Phosphodiesterase inhibitors
ACE-INHIBITORS
Enalapril; Benazepril; Ramipril
Used in cases of congestive heart failure; After starting furosemide
May be combined with Spironolactone
Also may be combined with Pimobendan
It is important to monitor the renal function!
TREATMENT OF CHRONIC CASES
§ Furosemide
§ Pimobendan
§ ↓ Neuroendocrine overcompensation
§ Potassium; Vitamin B
Emergency treatment of cardiological diseases?
Emergency Treatment of Cardiological Diseases
Diagnose ASAP; Immediate oxygen therapy
Top priorities:
§ ↓ Preload
§ ↓ Afterload
§ ↑ Myocardial contractility
§ Sedation
§ Treat life-threatening arrhythmias
Medication:
§ Furosemide + Pimobendan (vasodilator/inotrope) IV/PO
§ Sedation (if necessary): Butorphanol; Acepromazine
