cardiac failure is the commonest cause for hospital admission in those aged over 65 yrs
prevalence of CCF increases with increasing age and affects about 10% of the population older than 75 years.
in spite of significant advances in the treatment of heart failure, mortality rates remain high: 30 to 40 percent of patients with advanced disease and 5 to 10 percent of patients with mild symptoms die within five to 10 years.
there are two pathophysiologic types of CCF (or congestive heart failure (CHF))
systolic failure (impaired ability to contract) characterised by an ejection fraction < 45%
diastolic failure (impaired ability to fill in diastole) which is more poorly quantified and agreed criteria has not been reached
the two types have similar symptoms and signs and usually require echocardiography or angiography to discriminate.
diastolic heart failure is more common in women and elderly persons and accounts for 25-50% of patients hospitalised with cardiac failure.
although patients with diastolic heart failure have a lower annual mortality rate than patients with systolic heart failure, they have a higher rate than the general population.
Framington criteria for Dx of CCF
concurrent presence of either 2 major criteria or 1 major and 2 minor criteria:
major criteria
paroxysmal nocturnal dyspnea
weight loss of 4.5 kg in 5 days in response to treatment
neck vein distention
rales
acute pulmonary edema
hepatojugular reflux
S3 gallop
central venous pressure greater than 16 cm water
circulation time of 25 seconds
radiographic cardiomegaly
pulmonary edema, visceral congestion, or cardiomegaly at autopsy
minor criteria
nocturnal cough
dyspnea on ordinary exertion
a decrease in vital capacity by one third the maximal value recorded
pleural effusion
tachycardia (rate of at least 120 bpm)
bilateral ankle oedema
clinical features of CCF
symptoms
LV failure
SOBOE - most sensitive symptom but not specific
orthopnoae/PND - more specific but less sensitive (20-30% pts)
cough with pink, frothy sputum is highly suggestive
RV failure
SOA
signs
peripheral edema, jugular venous distention, and tachycardia are highly predictive of CCF but occur in only 10-20% pts.
other signs may also occur:
hypertension, cold & sweaty skin, pulsus alternans, wheezes, third or fourth heart sounds.
CXR only 80% sensitive
a negative BNP has 98% NPV
a positive BNP is non-specific but more useful if higher values in older people and intermediate pre-test probability - not helpful if low or high pretest probability
systolic heart failure
impaired ability of the ventricle to contract resulting in LV ejection fraction < 45%
The relaxation process has four identifiable phases:
isovolumetric relaxation from the time of aortic valve closure to mitral valve opening;
early rapid filling after mitral valve opening;
diastasis, a period of low flow during mid-diastole; and
late filling of the ventricles from atrial contraction
Diastole is a complex process that is affected by a number of factors, including:
ischemia
heart rate
heart rate determines the time that is available for diastolic filling, coronary perfusion, and ventricular relaxation.
velocity of relaxation
cardiac compliance (i.e., elastic recoil and stiffness)
hypertrophy
hypertrophied ventricle has a steeper diastolic pressure-volume relationship; therefore, a small increase in left ventricular end-diastolic volume (which can occur with exercise, for example) causes a marked increase in left ventricular end-diastolic pressure.
segmental wall coordination of the heart muscle.
aetiology of diastolic failure
hypertension
hypertension is the most common cause and causes LV hypertrophy and increased connective tissue content, both pf which decrease cardiac compliance.
ischaemia
Hypoxia inhibits the dissociation of myosin-actin crossbridges during muscle relaxation as this requires active transport of calcium ions into the sarcoplasmic reticulum.
tachycardia:
tachycardia adversely affects diastolic function by several mechanisms:
decreases left ventricular filling and coronary perfusion times
increases myocardial oxygen consumption
causes incomplete relaxation because the stiff heart cannot increase its velocity of relaxation as heart rate increases.
loss of the atrial “kick” in filling the ventricle
adverse effects of tachycardia (as above) if rapid ventricular rate
note that diastolic failure increases the risk of AF as the raised atrial pressures and distended atria predispose to AF developing.
systolic failure
residual blood within the ventricles at the end of systole decreases the pressure gradient between the atria and ventricles which thus impairs the rapid phase of early diastolic filling.
aging
increased collagen cross-linking, increased smooth muscle content, and loss of elastic fibers due to aging results in decreased ventricular compliance, increasing susceptibility to diastolic failure.
diagnosis of diastolic failure
generally requires 3 features:
symptoms and signs of cardiac failure (although these are rather non-specific features)
the presence of normal or mildly abnormal left ventricular systolic function (ejection fraction of greater than 45 percent)
HOWEVER, the presence of systolic failure does not exclude possible diastolic failure but does make it harder to definitively diagnose
evidence of abnormal left ventricular relaxation, filling, diastolic distensibility, or diastolic stiffness
on echocardiography, this may be suggested by either:
prolonged tau:
the time constant of LV pressure decay during isovolumetric relaxation which is a measure of LV stiffness
E-to-A wave ratio:
the ratio of peak velocities of blood flow during early diastolic filling (E wave) and atrial contraction (A wave) which is normally ~1.5.
the ratio falls to less than 1.0 in early diastolic dysfunction as stiffer heart relaxes more slowly.
As diastolic function worsens and left ventricular diastolic pressure rises, left ventricular diastolic filling occurs primarily during early diastole, because the left ventricular pressure at end-diastole is so high that atrial contraction contributes less to left ventricular filling than normal. This results in a rise in the E-to-A wave ratio which may rise higher than 2.0. This “restrictive pattern” confers a poor prognosis.
The E- and A-wave velocities are affected by blood volume and mitral valve anatomy and function. Furthermore, these wave velocities are less useful in the setting of atrial fibrillation.
E-to-A wave ratio > 2
on coronary angiography
Rx principles of diastolic failure
normalise blood pressure (to less than 130/85mmHg) to promote regression of LVH
consider dihydropyridine calcium channel blockers with care
The long-acting dihydropyridine class of calcium channel blockers is safe for use in patients with systolic heart failure, but nondihydropyridine agents should be avoided.