5. Heart failure (clinical aspects, medical therapy, emergency treatment of cardiac diseases) Flashcards

1
Q

Clinical aspects?

A

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

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2
Q

Aetiology?

A

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

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3
Q

Compensation of heart failure>

A

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

13

§ 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

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4
Q

Progression of cardiac failure?

A

PROGRESSION OF CARDIAC FAILURE

Myocardial damage; ↑ Congestion

§ RAAS becomes permanently activated

§ ↑ Heart rate

§ Insufficient oxygen & energy supply of cardiomyocytes

§ Endothelin release → Vasoconstriction; Myocardial

hypertrophy

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5
Q

Inflammation as a result of heart failure?

A

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

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6
Q

Cardiac remodelling?

A

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

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7
Q

Classification of heart failure left and right sided heart failure?

A

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

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8
Q

Cause of heart failure and medical therapy?

A

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

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9
Q

Emergency treatment of cardiological diseases?

A

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

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