DISCUSSION
Several studies showed a reduction in forced expiratory volume in the
first second (FEV1) and forced vital capacity (FVC) in heart failure
patients 8-11. Factors responsible for the restrictive
pattern are increased lung stiffness, respiratory muscle fatigue,
cardiac enlargement and constriction of under perfused alveoli leading
to reduced lung compliance in a low cardiac output state. Elsobkey and
Gomaa 12 showed that both valvular and ischemic
patients had lower than normal PFT results pre-operatively with a
predominant restrictive pattern. The authors also noticed that patients
with rheumatic heart disease had lower values compared to patients with
ischemic heart disease and this was explained by the fact that patients
with rheumatic heart disease are more prone to develop pulmonary
congestion in which the lung compliance is reduced and the resistance to
airflow is increased with resultant decreased gas exchange and pulmonary
function. This finding had also been confirmed in patients with mitral
valve disease by Saxena et al. 8. Importantly,
restrictive or obstructive lung impairment can be identified that is
solely due to cardiac decompensation in the absence of any intrinsic
lung disease 13.
The question is whether these reduced spirometry readings in surgical
patients represent a real risk for postoperative respiratory
complications or it is just a reflection of the heart failure status
that would improve postoperatively after fixing the surgical problem. In
order to answer this problem, we included in this study only coronary
patients with left ventricular dysfunction and patients with severe
left-sided valvular problems causing congestive heart failure. Despite
the small percentage of patients with a history of asthma or COPD in our
cohort, we demonstrated that the group of patients with moderate to
severe impairment of pulmonary function test has a significantly longer
duration of intubation and higher hospital mortality.
Our findings go in line with other studies that support the routine use
of PFT in cardiac surgery patients. In a prospective cohort study14, performing spirometry on all comers for cardiac
surgery irrespective of smoking or COPD history, preoperative spirometry
reclassified 18% of the patients. A reduced FEV1 independently doubled
the risk of death. They concluded that the inclusion of preoperative
spirometry in routine screening of cardiac surgical patients may improve
risk prediction and identify high-risk patients. Alam et al.15 observed that predicted FVC% and predicted FEV1%
were most strongly associated with poor postoperative outcomes including
postoperative respiratory failure, atelectasis and pulmonary infection
but not with postoperative mortality.
On the other hand, a small study by Spivak et al. 16and another one by Bando et al. 17, found that PFT
should not be used as exclusion criteria for CABG and that postoperative
cardiac function and occurrence of complications are more significant
than preoperative PFT in determining the duration of ventilation after
cardiac surgery and that routine spirometry is unnecessary for most
adult cardiac patients. Manganas et al. 18 found that
patients with severe COPD can undergo CABG without increased mortality
risk when compared with patients with normal PFT or with mild to
moderate COPD. However, they have an increased risk of pulmonary
infections, a tendency towards atrial fibrillation and slightly
increased length of hospital stay. Whether to add PFT and different
classifications of COPD to the STS risk model for predicting outcomes
after cardiothoracic surgery was studied by Ivanov et al.19 and it came with only little utility.