Cardiology

Cardiac failure

Cardiology Concepts

Definition: Heart failure means insufficient blood being pumped out to meet tissue demands despite a normal venous return. Most fo the time the issue is primarily due to weakness of the myocardium which may be due to several aetiologies. When the heart failaure is due to a myocardial issue these can be grouped into systolic and diastolic. The difference is not well explained but is easy if you think about it

Systolic failure: This is usually easier to understand. Imagine a water pump which is working at half energy. It will pump less per unit time and in the heart this is usually seen as a reduced ejection fraction. Can be due to muscle death or muscle hypoxia and the inability to generate satisfactory myocardial contractility. The issue is the ability of the heart muscle contraction.

Diastolic failure: This is due to inability of the ventricular muscle to relax. Filling the left ventricle is a bit like filling a balloon with air. With a well stretched compliant balloon you don't need to puff to hard to fill it. However a new or other balloon will be much stiffer and filling will be difficult. The problem is relaxation of muscle fibres. The left atrium will have to work harder to get blood in which can be seen as an increased LV end diastolic (filling) pressure. This is seen when the muscle is stiff and thick such as with severe LVH or HCM as well as older diabetic patients. Remember the balloon analogy - if because it is stiff and only half fills then there is going to be much less 'air' pumped out when you let it go and so there is failure. For diastolic dysfunction the management is largely diuretics and relaxants such as calcium antagonists.

Introduction

  • The Prognosis for severe cardiac failure is often worse than many cancers. LV systolic function largely determines prognosis.
  • In all cases of heart failure look for the aetiology and any exacerbating factors e.g. infection, fluid overload, arrhythmias, failure to takle medications etc.
  • Assess for treatable, transient and transplantable causes. Cardiac failure can worsen to become cardiogenic shock which has a very grave prognosis.

Definition

  • A clinical syndrome seen when heart fails to provide enough cardiac output to match needs despite sufficient venous return - "pump failure"

Terminology (see above)

  • Systolic failure - LV fails to eject enough blood per systole - usually a myocardial problem or valvular. e.g. AS, MR, Acute MI, Dilated CMP.
  • Diastolic failure - LV fails to fill properly during diastole due to increased LV end diastolic pressures. Usually due to stiff non relaxing myocardium - Hypertension, restrictive CMP, HCM, Elderly, Amyloid
  • Forward failure - low output, reduced renal, cerebral perfusion. Low volume pulse.
  • Backward failure - pulmonary oedema, peripheral oedema
  • High output - exceedingly rare Beri Beri, Paget's disease, Severe anaemia
  • Acute LVF - failure of the left ventricle as a pump
  • Left heart failure
  • Right heart failure
  • Congestive cardiac failure LHF + RHF

Causes

  • Ischaemic heart disease: Angina and Acute MI
  • Valvular heart disease: e.g. Aortic stenosis, mitral regurgitation
  • Hypertension heart disease (Phaeochromocytoma and Renal artery stenosis can provoke acute LVF)
  • Cardiomyopathy
    • Dilated (systolic)
    • Restrictive (diastolic)
    • Hypertrophic (diastolic)
    • Peripartum (systolic)
  • Arrhythmias e.g. Fast AF, VT
  • VSD, ASD
  • Myocarditis
  • Infective endocarditis
  • Toxins
  • Thyroid disease, Acromegaly
  • Congenital heart disease

Clinical classification of severity

  • Class I: No symptoms
  • Class II: Symptoms with moderate exertion
  • Class III: Symptoms with moderate exertion
  • Class IV Symptoms at rest

Clinical signs

  • Left heart failure
    • Breathless, distressed, Cyanosed
    • Orthopnea, Paroxysmal nocturnal dyspnoea
    • Tachycardia, Pulsus alternans, Gallop rhythm S3
    • Bibasal crepitations
    • Bat wings pulmonary oedema on CXR
  • Right heart failure
    • Elevated JVP
    • Hepatomegaly (pulsatile if TR) ascites and even a coagulopathy and deranged LFTs
    • Peripheral oedema
    • Parasternal heave
    • Nocturia due to redistribution of fluid at night
    • Pleural effusion (Right sided usually)
  • Biventricular - both RHF + LHF

Investigations

  • FBC: anaemia can worsen heart failure usually when Hb < 7-8 g/dl
  • ECG : Change with hypertension, IHD
  • U&E : Low sodium is a poor prognostic signs and may be due to many causes, Low Potassium should be avoided but may be seen with loop diuretics. Consider combining with potassium sparing drug. Beware hyperkalaemia especially with potassium sparing diuretics and ACEI.
  • Brain naturietic peptide (BNP): level parallels heart failure
  • CXR - upper lobe blood diversion, Kerly B lines, Cardiomegaly, effusion
  • Echo - quickly determines LV function and valves
  • Angiography - if IHD is suspected to be the underlying cause

Management of Acute LVF

  • Sit patient up and give oxygen 35% or higher if no risks
  • Furosemide 50-100 mg iv
  • Consider Continuous positive airways pressure (CPAP)
  • Diamorphine 2.5-5 mg IV state (Morphine 5-10 mg IV)
  • Sublingual GTN and/or IV Nitrates if SBP > 100 mmHg
  • Control rate with Digoxin if AF. Amiodarone
  • Venesection if in extremis and Hb > 10g/dl though it has fallen out of favour
  • Look for and treat cause

Chronic Management of Congestive cardiac failure

  • Stop smoking. Low salt diet. Weight loss if obese.
  • Good Hypertension control
  • Revascularisation if needed if IHD (Stent/CABG)
  • Optimal diabetic management
  • Diastolic failure and HCM - avoid inotropes and digoxin. Give diuretics/calcium channel blockers
  • Diuretics
    • Loop e.g. Furosemide 20-200 mg od or in divided doses
    • Thiazide diuretics. Metolazone is particularly potent
    • Potassium sparing- Spironolactone : only diuretic with mortality evidence
  • Digoxin
    • Particularly useful in AF
    • Reduction in hospitalisation but no mortality benefit shown
    • Dose 62.5 mcg od to 250 mcg od
    • Avoid hypokalaemia. Cautious use in renal failure.
    • Drug of choice also with diastolic dysfunction
  • ACE Inhibitors/ ARB
    • Improve outcome and reduce mortality
    • Ramipril 1.25 - 10 mg po daily
    • ACE can cause cough, angiooedema and renal dysfunction
  • Beta blockers
    • Used for systolic heart failure once fluid overload corrected
    • Slowly up-titrate dosage.
    • Carvedilol or metoprolol
  • Calcium channel blockers
    • For those with diastolic failure
  • Warfarin
    • Used in AF or LV thrombus.
    • Can be used in Dilated CMP but evidence of benefit lacking
  • Biventricular pacing
    • Pacing wire into RV and LV to synchronise function
    • Those with QRS > 120 ms and SR and Moderate to severe HF
  • Implantable cardioverter defibrillator
    • Selected groups at high risk of mortality
  • Cardiac transplant
  • Aspirin 75 mg od if IHD
  • Statin if IHD
  • Referral to cardiac function clinic and support from cardiac failure nurses can help uptitrate medications and support patient post discharge.

Cardiogenic Shock

Introduction

  • Cardiogenic shock is when the heart is unable to produce sufficient cardiac output to match general systemic metabolic requirements and to maintain a blood pressure over SBP > 90 mmHg despite sufficient venous return. The problem lies with the heart and sepsis and other causes of hypotension have been excluded. Mortality is about 70% unless there is any easily remedial treatable cause e.g. Large MI and angioplasty and reestablishment of coronary perfusion
  • Shock is not a diagnosis but a clinical syndrome of organ hypoperfusion. Cardiogenic shock is when the aetiology is primarily cardiac. Shoch itself causes further shock, the prognosis is very poor but where there is an underlying treatble aetiology improvement can be marked otherwise there is an inexorable decline and death. Make sure cardiogenic shock is not misdiagnosed RV infarction needing filling or a tamponade needing draining. Echocardiography is often key.
  • Clinical Findings include systemic hypotension (systolic BP < 90 mmHg) and if measured an increased pulmonary capillary wedge pressure > 18 mmHg. Renal hypoperfusion leads to oliguria with urinary output < 20 ml/hour. Reduced cardiac output (reduced cardiac index) leads to systemic hypoperfusion and in severe cases the patient is severely vasoconstricted and cerebrally obtunded due to cerebral hypoperfusion. General organ hypoperfusion leads to lactic acidosis.

Aetiology : a cause or causes should be looked for and managed.

  • Myocardial disease: Myocardial infarction - classically Anterior STEMI, Myocarditis, Worsening Cardiomyopathy
  • Valve failure - Acute MR, Acute VSD, Aortic regurgitation
  • Toxins : Verapamil overdose, Excess Beta blocker and other negative inotropes
  • Congenital heart disease: Neonates and infants
  • Arrhythmias : Ventricular tachycardia, Fast Atrial fibrillation, Complete Heart block

Investigations

  • FBC: anaemia may suggests bleeding or if long standing reduced oxygen carrying capacity. Transfusion may be indicated at least to get a Hb > 8g/dl
  • U&E: renal function is useful to assess for acute kidney injury
  • ECG: look for acute evidence of MI or arrhythmia. ECG with right-sided chest leads may document RV infarction which can be improved with IV fluids. If ST elevation is found then urgent reperfusion strategies should be pursued in haste.
  • Measure serum lactate - of some prognostic value and may suggests a degree of severity value
  • CXR - cardiomegaly and oedema suggests a primary cardiac problem.
  • Echocardiogram is by far the most useful test beyond ECG and even a bedside echo can be invaluable to determine if this is a myocardial or valvular problem. An assessment of LV function is crucial.
  • Septic screen - sepsis and cardiogenic chock may coexists. Blood cultures if valve endocarditis suspected
  • Troponin may be elevated slightly or markedly if there is infarction and may have some prognostic use
  • ECG is critical in diagnosing arrhythmias or STEMI
  • Measure urinary output can be an indirect marker of renal perfusion and cardiac output
  • Consider need for CVP or Swan Ganz catheter if they add value, can be done quickly and aseptically and do not cause too much haemodynamic stress to the patient. Less commonly used nowadays. Surrogate clinical markers often sufficient and blind following of catheter measurements in faulty equipment or technique has lead to poor outcomes. Should at least be reserved for the HDU/ITU setting and not the Medical ward.

Management

  • Primary PCI (or thrombolysis) for Acute STEMI (have seen moribund patients come back from the brink of death with reperfusion and an anterior STEMI or LBBB)
  • (DD) Dobutamine if SBP > 90 mmHg and Dopamine if SBP < 90 mmHg has been recommended. Inotropes have no evidence base and may actually increase myocardial oxygen demand which could exacerbate the situation. Use with caution and careful monitoring.
  • Pacemaker for Bradycardia
  • IV Nitrates may be used but very careful titrated with BP
  • Treat also as ACS if applicable
  • Surgery for acute MR/VSD should be done early
  • Intra-aortic balloon pump is useful for all except Acute AR which it worsens as a bridge to further assessment and definitive treatment
  • Left-ventricular assist devices (LVAD) may be used in selected patients with refractory shock as a bridge to cardiac transplantation

Inotropes


Vasoconstriction Inotrope Heart Rate Vasodilation
Low Dose Dopamine 0 ++ ++ ++
High Dose Dopamine +++ ++ ++ ++
Low Dose Dobutamine 0 ++++ + ++
High Dose Dobutamine ++ ++++ + ++
Noradrenaline ++++ ++ 0 0
Adrenaline ++++ ++++ ++++ +++

Intra aortic balloon pump (IABP)

This is a mechanical device to augment coronary and cerebral perfusion. Consists of a balloon 35-50 ml placed via femoral artery catheter in aorta just distal to left subclavian artery. There is controlled timed Helium inflation of the balloon during diastole. Increased diastolic aortic pressures (coronary perfusion)

Indications: Bridging procedure to transplant with end stage heart failure, management of cardiogenic shock/Acute LVF, Refractory unstable angina. Contraindications: Aortic regurgitation, Aortic aneurysm, Severe aorto-iliac disease. Complications: Aortic dissection, Lower limb ischaemia