CONGESTIVE HEART FAILURE (CHF) : A BRIEF REVIEW

Congestive Heart Failure - Diastolic

Introduction

Congestive heart failure (CHF) occurs when the cardiac output is not adequate enough to meet the demands of the body. This can occur for several reasons as congestive heart failure is the predominant clinical presentation in multiple disease states. Heart failure can be due to:

Systolic dysfunction (reduced ejection fraction)Diastolic dysfunction (relaxation or filling abnormality)Valvular heart diseaseRight heart failureArrhythmiaHigh output CHF (i.e. severe anemia, arteriovenous malformations)

Review of diastolic congestive heart failure will be presented here. Review of systolic congestive heart failure, valvular heart disease, right heart failure and high output heart failure are presented elsewhere.

Pathophysiology

Diastolic dysfunction occurs when the left ventricular myocardium is non-compliant and not able to accept blood return in a normal fashion from the left atrium. This can be a normal physiologic change with aging of the heart or result in elevated left atrial pressures leading to the clinical manifestations of diastolic congestive heart failure.

While there is some degree of activation of the sympathetic nervous system and the renin-angiotensin-aldosterone system (RAAS) in states of diastolic heart failure, it is not as dramatic as seen with systolic heart failure. Also, these neurohormonal systems do not exert the negative remodeling effect on the heart during diastolic heart failure as much as occurs with systolic congestive heart failure. Below is a schematic of the neurohormal mechanisms present in congestive heart failure:

Etiology

There are a number of causes of diastolic congestive heart failure:

Hypertensive heart diseaseAging of the heartRestrictive cardiomyopathyValvular heart diseaseTachyarrhythmiasConstrictive pericarditis

Hypertension causes left ventricular hypertrophy and impaired relaxation. Over time, this progressing resulting in higher degrees of diastolic dysfunction, low cardiac output and symptoms of congestive heart failure.

The aging process of the heart is not well understood, however fibrotic changes are seen within the myocardium. This results in a relaxation abnormality that is almost universally present by the age of 60. In the elderly, this can progress causing significant diastolic impairment and congestive heart failure.

Restrictive cardiomyopathies frequently cause deposition of substances (i.e. amyloid protein) within the myocardium causing diastolic relaxation abnormalities and when severe, diastolic congestive heart failure.

Valvular heart disease such as mitral stenosis, technically causes heart failure due to diastolic dysfunction of the left ventricle. Severe aortic stenosis causes left ventricular hypertrophy and when left ventricular pressures increase a significant amount, diastolic heart failure can occur.

When a tachyarrhythmia occurs such as atrial fibrillation with an uncontrolled ventricular response, congestive heart failure can occur in the setting of normal systolic function from a shortened diastolic filling time. This is technically a form of diastolic heart failure, however once ventricular rates are controlled, the cardiac hemodynamics should dramatically improve.

Symptoms

The general symptoms of congestive heart failure are the same regardless of the etiology (systolic or diastolic) and are attributed to either fluid retention (related to the activated RAAS) or low cardiac output. They can also be categorized as from left heart failure versus right heart failure.

Left heart failure will result in low cardiac output symptoms and transmission of the increased left-sided cardiac pressures into the lungs causing pulmonary edema and a sense of dyspnea. With physical exertion the heart demands increased cardiac output which is not able to be satisfied in states of heart failure and thus left heart pressures increase significantly causing this transient pulmonary edema.

As those increased pressures from the left heart affect the right ventricle, right heart failure can ensue. The most common cause of right heart failure is left heart failure.
Right heart failure symptoms include lower extremity dependant edema. When the legs are elevated at night, the fluid redistributes centrally causing pulmonary edema resulting in orthopnea (dyspnea while laying flat) or paroxysmal nocturnal dyspnea (PND). Hepatic congestion can occur causing right upper quadrant abdominal pain.

Symptoms related to low cardiac output include fatigue, weakness and in extreme cases, cardiac cachexia can occur.

The New york Heart Association (NYHA) functional class helps to classify patients based on their symptoms of heart failure.

Class I: No symptoms of heart failure
Class II: Symptoms of heart failure with moderate exertion such as ambulating 2 blocks or 2 flights of stairs
Class III: Symptoms of heart failure with minimal exertion such as ambulating 1 block or 1 flight of stairs, but no symptoms at rest
Class IV:  Symptoms of heart failure at rest

Note that the NYHA functional class differs from the ACC/AHA heart failure classification system in that the former allows movement from one class to the other while the ACC/AHA classification does not (see below).

Diagnosis

Echocardiography is the gold standard to diagnose diastolic dysfunction. There are four grades of diastolic dysfunction as described below. Clinical manifestations of congestive heart failure may start to occur once grade II diastolic dysfunction is present, however not in the presence of grade I diastolic dysfunction (impaired relaxation).

Grade I (impaired relaxation): This is a normal finding and occurs in nearly 100% of individuals by the age of 60. The E wave velocity is reduced resulting in E/A reversal (ratio < 1.0). The left atrial pressures are normal. The deceleration time of the E wave is prolonged measuring > 200 ms. The e/e’ ratio measured by tissue Doppler is normal.

Grade II (pseudonormal): This is pathological and results in elevated left atrial pressures. The E/A ratio is normal (0.8 +- 1.5), the deceleration time is normal (160-200 ms), however the e/e’ ratio is elevated. The E/A ratio will be < 1 with Valsalva. A major clue to the presence of grade II diastolic dysfunction as compared to normal diastolic function is the presence of structural heart disease such as left atrial enlargement, left ventricular hypertrophy or systolic dysfunction. If significant structural heart disease is present and the E/A ratio as well as the deceleration time appear normal, suspect a pseudonormal pattern. Valsalva distinguishes pseudonormal from normal as well as the e/e’ ratio. Diuresis can frequently reduce the left atrial pressure relieving symptoms of heart failure and returning the hemodynamics to those of grade I diastolic dysfunction.

Grade III (reversible restrictive): This results in significantly elevated left atrial pressures. Also known as a “restrictive filling pattern”, the E/A ratio is > 2.0, the deceleration time is < 160 ms, and the e/e’ ratio is elevated. The E/A ratio changes to  < 1.0 with Valsalva. Diuresis can frequently reduce the left atrial pressure relieving symptoms of heart failure and returning the hemodynamics to those of grade I diastolic dysfunction.

Grade IV (fixed restrictive): This indicates a poor prognosis and very elevated left atrial pressures. The E/A ratio is > 2.0, the deceleration time is low and the e/e’ ratio is elevated. The major difference distinguishing grade III from grade IV diastolic dysfunction is the lack of E/A reversal with the Valsalva maneuver (no effect will be seen with Valsalva). Diuresis will not have a major effect on the left atrial pressures and clinic heart failure is likely permanent. Grade IV diastolic dysfunction is present only in very advanced heart failure and frequently seen in end-stage restrictive cardiomyopathies such as amyloid cardiomyopathy.

Treatment

There is a relative lack of data to guide medical therapy in patients with diastolic congestive heart failure, especially when compared to systolic congestive heart failure.

The ACC/AHA guidelines give three class I recommendations to medically treat chronic diastolic congestive heart failure.

The first is to control the heart rate in patients with atrial fibrillation in order to improve diastolic filling. Tachycardia shortens diastolic filling time and so keeping heart rates < 100 beats per minute and preferably between 60-80 beats per minute will improve cardiac output when significant diastolic heart failure is present. Rate control can be achieved using beta-blockers, non-dihydropyridine calcium channel blockers, or digoxin.

The second recommendation is to control systolic and diastolic blood pressure using the standard treatment for hypertension.

The third is to use diuretics to control pulmonary congestion and peripheral edema.