Severe Heart Failure

82 Severe Heart Failure

Eduard Shantsila, Benjamin Wrigley, Michael D. Sosin, Gregory Y.H. Lip

Heart failure is a very common condition with high mortality and morbidity rates. Data from the Framingham heart study suggest that at 40 years of age, the lifetime risk for congestive heart failure is 21.0% (95% confidence interval [CI], 18.7%-23.2%) for men and 20.3% (95% CI, 18.2%-22.5%) for women.¹ The prevalence of heart failure is between 2% and 3% and reaches 10% and 20% in those older than 70 years.² In the United States, approximately 5 million patients have heart failure, with over 550,000 new cases diagnosed each year.³ Despite improvements in treatment, the overall prevalence of heart failure is increasing because of the aging of the population and better survival following myocardial infarction (MI).^3,⁴ Total heart failure–related costs were about $28 billion in 2005 and consume approximately 2% of national expenditure on health in Europe.⁵ Patients with severe heart failure often present in extremis, and their condition may deteriorate rapidly, so a sound knowledge of immediate treatment is vital for critical care and emergency physicians. Such patients often respond rapidly to appropriate treatment, making this a very satisfying condition to treat. However, it is important to note that outlook remains poor despite initial clinical improvement.

In this chapter, we will discuss causes, presentation, investigation, treatment, and prognosis of severe heart failure, including new developments in the investigation and management of this common, serious condition.

Etiology

Ischemic heart disease is the most common cause of heart failure, commonly related to previous MI. Although epidemiologic surveys such as the Framingham study suggest a high prevalence of hypertension as the “cause” of heart failure, it is likely that associated ischemic heart disease or arrhythmias also contribute. Other studies have demonstrated similar findings (Table-82-1).

TABLE 82-1 Epidemiologic Studies of Etiology of Heart Failure

It should be pointed out that epidemiologic studies such as the Framingham study have been almost exclusively carried out in white populations, and etiologic factors may have different relative importance in other ethnic groups. For example, in Afro-Caribbeans, hypertension is the predominant etiologic factor, whereas in Indo-Asians, coronary artery disease and diabetes are common. It is important to note that different causes may coexist in the same patient.

Ischemic Heart Disease

Ischemic heart disease is the most common cause of heart failure in the Western world. Many patients presenting with severe heart failure will give a history of previous MI. However, an episode of severe heart failure may also be the first manifestation of ischemic heart disease, either due to massive MI causing cardiogenic shock ⁶ or as a result of previous silent (or unreported) episodes of ischemia/infarction. It is therefore important to exclude MI in all patients presenting with severe heart failure. Additionally, once the patient is stabilized, adequate secondary preventive strategies are vital to prevent further ischemia or infarction. Some patients with ischemic cardiomyopathy may show evidence of “hibernation” of segments of myocardium,⁷ and cardiac function in these patients may improve with revascularization (see later discussion).

Hypertensive Heart Disease

Hypertension causes a significant proportion of cases of heart failure. An episode of severe heart failure may be the first presentation of hypertension—such patients have had unrecognized severe hypertension for many years. The onset of heart failure may result in a previously raised blood pressure becoming normal or even low, which can make the diagnosis difficult in a patient with previously undiagnosed hypertension. Electrocardiography and echocardiography may show evidence of left ventricular hypertrophy. Patients with hypertension also commonly have diastolic dysfunction as a cause for heart failure. In this situation, systolic contraction is normal or minimally impaired, but the main abnormality is in diastolic relaxation and ventricular compliance. The incidence of diastolic abnormalities increases with age, and while the mortality rate associated with diastolic heart failure appears to be lower than that of systolic heart failure, it is still significant. To date, the ideal method of defining abnormal diastolic function has not been clearly ascertained.

Dilated Cardiomyopathy

Dilated cardiomyopathy is defined as left ventricular dysfunction of unknown cause. It is therefore a diagnosis of exclusion, and a firm diagnosis of dilated cardiomyopathy can only be made in the presence of a normal coronary angiogram. Intensive investigation of patients with a label of dilated cardiomyopathy may yield a definite cause in at least 50% of cases (Table 82-2). As many as 30% of patients with dilated cardiomyopathy may have a genetic cause of the disease.⁸

TABLE 82-2 Final Diagnoses in 1230 Patients with Initially Unexplained Cardiomyopathy

Diagnosis	Number	Percentage
Idiopathic dilated cardiomyopathy	616	50
Myocarditis	111	9
Ischemic heart disease	91	7
Infiltrative cardiomyopathy	59	5
Peripartum cardiomyopathy	51	4
Hypertension	49	4
Human immunodeficiency virus infection	45	4
Connective tissue disease	39	3
Substance abuse	37	3
Familial	25	2
Valvular disease	19	1.5
Doxorubicin therapy	15	1
Endocrine disorder	11	1
Others	62	5.5

Data from Felker GM et al. Underlying causes and long term survival in patients with initially unexplained cardiomyopathy. N Engl J Med 2000;342:1077-84.

Dilated cardiomyopathy can manifest at any age, and because heart failure may be perceived as a disease of the elderly, this can often result in misdiagnosis in younger patients.

Valvular Heart Disease

Structural Valve Disease

Valvular heart disease was once a leading cause of heart failure in the Western world. Owing to the rise in ischemic heart disease and the decrease in rheumatic fever, it is now less often the primary cause of an episode of severe heart failure. However, it is important not to discount significant valve disease in patients presenting with severe heart failure and to remember that signs may be difficult to elucidate in the acutely ill patient. Because all patients with severe heart failure should undergo echocardiography soon after admission, most if not all cases of significant valve disease should be detected. As noted earlier, after extensive MI, acute mitral regurgitation can develop, causing sudden-onset severe heart failure days after a patient’s initial presentation with chest pain.

Functional Valve Disease

Patients with heart failure of any cause with dilation of the left ventricle and mitral valve ring can develop functional mitral regurgitation. This further reduces left ventricular performance; in selected patients, mitral valve repair or replacement may be indicated.

Diabetes

In addition to the role of diabetes as a risk factor for the development of ischemic heart disease and resultant heart failure, there is evidence for a distinct diabetic cardiomyopathy.⁸ Current guidelines recognize diabetes as a risk factor for heart failure.⁸ Hemoglobin A_1c levels have been shown to be an independent progressive risk factor for cardiovascular and total mortality and rehospitalization rate in heart failure patients.^9,¹⁰ All patients presenting with heart failure should be screened for diabetes, both for this reason and so that appropriate secondary prevention can be instituted.

Other Possible Causes or Exacerbating Factors

Rare causes of heart failure must always be considered, especially in younger patients, and these include amyloidosis and hemochromatosis. Another important cause is human immunodeficiency virus (HIV) infection, and HIV-associated cardiomyopathy has been well described. Given that HIV infection is considered pandemic by the World Health Organization, many more patients may present in this way in the future.

Patients with a long history of stable heart failure may decompensate as the result of a number of different factors. Intercurrent infection is a common cause of decompensation, and prompt recognition and treatment are important. Arrhythmias are also a common cause for decompensation of a previously stable heart failure patient, and a recent meta-analyses of 16 randomized clinical trials (53,969 patients) revealed that the presence of AF is associated with an adverse effect on total mortality, with an odds ratio of 1.40 (95% CI, 1.32-1.48).¹¹ Another common cause of decompensation is anemia, which is often poorly tolerated in patients with heart failure. A meta-analysis of 34 studies comprising 153,180 patients, of whom 37.2% were anemic, showed that adjusted mortality risk of anemia had a hazard ratio of 1.46 (95% CI, 1.26-1.69).¹² Poor prognosis associated with presence of atrial fibrillation or anemia was irrespective of left ventricular systolic function, either preserved or impaired.^11,¹² It is vital to consider and treat such exacerbating conditions where appropriate.

Presentations of Severe Heart Failure

Severe heart failure can manifest in several ways. The patient may or may not have a previous history of heart failure or precipitating conditions such as angina or hypertension. It is important to note that gradual-onset heart failure can easily be mistaken for asthma, and patients presenting to an emergency department may well have been given a diagnosis of asthma in the weeks or months preceding their admission.

Acute Presentation: Pulmonary Edema

The classic presentation of heart failure is with acute pulmonary edema. Such patients present with extreme shortness of breath, often unable to speak because of their rapid respiratory rate. Symptoms may come on very suddenly. Even patients with ischemic heart failure may not report chest pain, either because the ischemia is silent or because the pain is being masked by the profound shortness of breath. Many patients will be unable to give a history owing to their shortness of breath, and therefore examination findings and basic investigations are vital to make the diagnosis.

Subacute Presentation: Shortness of Breath/Peripheral Edema

Many patients with severe heart failure present less acutely with varying combinations of breathlessness and edema. This is often the case in patients with a previous diagnosis of heart failure and can be precipitated by intercurrent infection or withdrawal of diuretic or other medication (by the patient or a physician). In the early stages, edema may be more prominent unilaterally, and this may result in diagnostic difficulty. Such patients may be referred for exclusion of deep venous thrombosis (and it is important to be aware that the two conditions can coexist). These patients often report gradually increasing breathlessness with symptoms of orthopnea (shortness of breath occurring when lying supine) and paroxysmal nocturnal dyspnea (sudden shortness of breath waking the patient from sleep). Patients may resort to sleeping in a chair, leading to additional gravitational edema. Edema of the bowel can lead to reduced appetite, so called “cardiac cachexia,” and further edema from hypoproteinemia. Peripheral edema is therefore often multifactorial in patients with heart failure. Differential diagnoses of peripheral edema are listed in Table 82-3.

TABLE 82-3 Causes of Peripheral Edema

Examination findings are similar to those for the acute presentation, although the patient is not in extremis and is able to speak sufficiently to give a full history. A full examination is possible more often in this situation, including auscultation of the heart sounds and abdominal examination. Peripheral edema may well be extensive, up to the abdominal wall and sacral areas. The jugular venous pulse may be elevated. Patients with extensive peripheral edema but a low jugular venous pulse may have hypoproteinemia rather than heart failure.

Chest Pain

As noted earlier, ischemic heart disease is an extremely common cause of heart failure. Patients presenting with chest pain thought to be ischemic in nature must be examined closely for subtle signs of heart failure. Patients presenting with extensive MI may develop symptoms and signs of heart failure hours or days after admission. This may be precipitated by treatment (such as acute use of beta-blockers or calcium channel blockers) or by a complication of the MI, such as ventricular septal defect or mitral valve prolapse due to chordal rupture.

Collapse/Cardiac Arrest

Patients with severe heart failure of any cause are at high risk for malignant arrhythmias and thromboembolic disease such as pulmonary embolism. It is therefore not unusual for patients with severe heart failure to present with collapse or cardiac arrest. In such patients, the outlook is extremely poor. Even for patients presenting with ventricular tachycardia or ventricular fibrillation who are successfully cardioverted, the chance of surviving to discharge from hospital is low. Such patients can be considered for implantable cardioverter-defibrillators (see later and Chapter 81). Pulmonary embolism and ventricular arrhythmias are covered in Chapters 62 and 79, respectively, so will not be discussed in detail here.

Investigations

Electrocardiography

All patients presenting with severe heart failure require at least one electrocardiogram (ECG). In cases of diagnostic difficulty, an entirely normal ECG virtually excludes systolic heart failure as the cause of symptoms.¹⁴ In heart failure, an ECG is essential to diagnose arrhythmias such as atrial fibrillation, which may complicate management, as well as to look for evidence of myocardial ischemia or infarction and conduction abnormalities such as left bundle branch block or bradycardia due to high-degree atrioventricular block, which may respond to pacing. In patients in whom ischemia is suspected, serial ECGs are recommended, as changes may evolve during the course of the patient’s treatment. Patients with acute severe heart failure should have continuous ECG monitoring during the acute phase, as they are at high risk for malignant ventricular arrhythmias. Patients with biventricular pacemakers (discussed later) in situ may have paced QRS complexes that are narrower than in those with single-chamber right ventricular leads.