Congestive heart failure natural history
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Heart failure is associated with significantly reduced physical and mental health, resulting in a markedly decreased quality of life. Congestive heart failure is also associated with a poor prognosis. With the exception of heart failure caused by reversible conditions, the condition usually worsens with time. Although some people survive many years, progressive disease is associated with an overall annual mortality rate of 10%. In the Framingham experience, 80% of men and 70% of women with heart failure who were under 65 years of age had died within 8 years of the diagnosis.
1. Cardiac Arrhythmias:
- Ventricular tachycardia and ventricular fibrillation can occur as serious complications of heart failure when its pump function is severely impaired. This further worsens the cardiac output and even possible death.
- Atrial fibrillation which is rapid beating of atrium without optimal forward pumping of blood is another complication of heart failure which occurs as a result of resistance to blood flow from atrium to ventricles. These patients are at increased risk of stroke.
- Left bundle branch block is an abnormality in electrical conduction in the heart.
2. Pulmonary Congestion:
- Pulmonary congestion which occur in left ventricular failure can cause pulmonary edema.
- Venous stasis and pedal edema can occur as a complication of right heart failure. These conditions predispose patients to venous ulcers, infections and cellulites.
- Cardiac cirrhosis occurs as a result of hepatic venous congestion. This can lead to coma and even death .
3. Angina and myocardial infarction: Cardiac ischemia and infarction can also occur when heart failure patients undergo exertion. With LV dilation, LV wall stress increases, and this increases the risk of angina. Autopsy studies demonstrate that plaque rupture and coronary thrombosis is a common mode of death in patients with congestive heart failure.
4. Renal failure: Renal impairment can occur secondary to decreased renal perfusion. This further worsens heart failure by fluid retention.
Risk Stratification Tools
The prognosis in patients with heart failure can be assessed using a variety of risk stratification tools and cardiopulmonary exercise testing. Clinical prediction rules use a composite of clinical factors such as lab tests and blood pressure to estimate prognosis. Among several clinical prediction rules for assessing the prognosis in acute heart failure, the 'EFFECT rule' slightly outperformed other rules in stratifying patients and identifying those at low risk of death during hospitalization or within 30 days. Other simpler methods for identifying low risk patients include the:
- ADHERE Tree rule which indicates that patients with blood urea nitrogen < 43 mg/dl and systolic blood pressure at least 115 mm Hg have less than 10% chance of inpatient death or complications.
- BWH rule indicates that patients with systolic blood pressure over 90 mm Hg, respiratory rate of 30 or less breaths per minute, serum sodium over 135 mmol/L, no new ST-T wave changes have less than 10% chance of inpatient death or complications.
A very important method for assessing prognosis in advanced heart failure patients is cardiopulmonary exercise testing (CPX testing). CPX testing is usually required prior to heart transplantation as an indicator of prognosis. Cardiopulmonary exercise testing involves measurement of exhaled oxygen and carbon dioxide during exercise. The peak oxygen consumption (VO2 max) is used as an indicator of prognosis. As a general rule, a VO2 max less than 12-14 cc/kg/min indicates a poor survival and suggests that the patient may be a candidate for a heart transplant. Patients with a VO2 max<10 cc/kg/min have clearly poorer prognosis. The most recent International Society for Heart and Lung Transplantation (ISHLT) guidelines also suggest two other parameters that can be used for evaluation of prognosis in advanced heart failure, the heart failure survival score and the use of a criterion of VE/VCO2 slope > 35 from the CPX test. The heart failure survival score is a score calculated using a combination of clinical predictors and the VO2 max from the cardiopulmonary exercise test.
Mortality Associated with Heart Failure
Based on the 44-year follow-up of the NHLBI’s Framingham Heart Study:
- 80% of men and 70% of women under age 65 who have heart failure will die within following 8 years.
- In people diagnosed with heart failure, sudden cardiac death occurs at 6 to 9 times the rate of the general population.
- One in eight deaths has heart failure mentioned on the death certificate.
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