In our study, cardiac asthma represented one third of CHF in elderly patients. Despite a higher percentage of hypercapnic acidosis in the cardiac asthma group, patients presented similar short and long term prognoses. Cardiac asthma patients exhibited greater peripheral airflow obstruction as shown by the reduced forced expiratory flow-rates at low lung volumes (Table 2)
Multiple studies have investigated the effects of CHF on lung mechanics. Patients with chronic CHF and orthopnea have a considerable increase in airflow resistance upon adopting the supine posture associated with supine expiratory flow limitation [22, 23]. Patients with chronic, predominantly nonvalvular CHF frequently exhibit a restrictive ventilatory defect, due to enlarged heart size, increased intrathoracic fluids, and impaired inspiratory muscle strength . While a restrictive defect may be seen in patients with both chronic heart failure (HF) and acute CHF, significant airflow obstruction is more likely to occur in the latter. Airway obstruction can occur during CHF through various mechanisms and with various degrees of severity [11–13, 23–25]. Indeed, CHF can mimic acute asthma, a circumstance commonly referred to as "cardiac asthma." Pulmonary function studies have demonstrated increased airway resistance or decreased forced expiratory flows in CHF. The existence of dysfunction in small airways in CHF is suggested by an increased closing volume. Studies have suggested that with severe left HF there was a significant narrowing of the large airways. Finally, some patients with HF, when challenged with methacholine, exhibit nonspecific bronchial hyperresponsiveness. However, the majority of these studies did not clearly distinguish smokers from nonsmokers, a history of thoracic surgery, or significant obesity. Obstructive changes tend to be mild and appear to be more prevalent during periods of acute decompensation of CHF. They tend to improve with diuresis presumably due to a reduction in extravascular lung water, and a general reduction in pulmonary and bronchial blood volumes . There also may be an enhanced degree of airway reactivity that diminishes with diuresis. Small improvements in expiratory flows are observed with anticholinergic and β2-agonist drugs in patients with chronic heart failure. Thus, data about the best treatments for cardiac asthma (i.e. are bronchodilators useful ?) are still lacking [16, 26–30].
Wheezing is a frequent physical examination abnormality, common with acute asthma, exacerbation of COPD, and cardiac asthma. In the latter, wheezing is integrated in the Boston criteria for CHF, a clinicoradiographic validated score . The prevalence of cardiac asthma has not been specifically reported in studies of heart failure. Nevertheless, recent studies found the rate of wheezing to be 10-15% in non-elderly patients with HF [2, 6, 31, 32]. We demonstrated a high rate of cardiac asthma (35%) in elderly patients. Our study suggests that emergency physicians should focus on past diagnosis of COPD in patients with CHF and cardiac asthma, especially in those presenting with hypercapnia.
The population in our study of acute heart failure in elderly patients seems similar to previous studies in term of past medial history and prognosis. The in-hospital mortality was 22 %, compared to a mortality ranging from 13% to 29 % in other studies [2–8]. The rate of admission at 3 months was 42% close to a rate of early rehospitalization from 29 to 47%, within 3 to 6 months of the initial discharge [1, 7, 8]. Both groups had a similar prognosis (Fig. 1). Indeed, one could assume that cardiac asthma had a better prognosis because auscultation revealed fewer crackles, which could suggest less alveolar edema . However, patients with cardiac asthma had higher hypercapnic acidemia which is thought to be associated with worse prognosis . In fact, the usual variables for assessing severity (respiratory rate, PaO2, median values of BNP, rate of non systolic heart failure) confirmed similar severity of CHF in both groups.
The method used in our study to diagnose CHF and COPD requires further comment. For the diagnosis of CHF there is no ideal standard. Thus, as in several previous studies, we used consensus diagnosis by experts to assess the final diagnosis of CHF supported with results of Doppler-echocardiography when available during hospitalization , and BNP and NT-proBNP levels performed blindly at admission in the emergency room when available . As in most ED, Doppler-echocardiography was not immediately available. It was performed in 72% of elderly patients in our institution, and PFTs were performed in 67 (32%) patients, with a mean time from admission to PFT of 6 days. These investigations could not been obtained in all patients, and we could not report lung volumes measured by pletysmography.