Pathophysiologic features of pulmonary thromboembolism in man

Prognostic Value of Arterial/Alveolar Oxygen Tension Ratio (a/APO2) in Acute Pulmonary Embolism

BACKGROUND

Because the arterial/alveolar oxygen tension ratio (a/APO2) is relatively constant throughout the entire range of fractional inspired oxygen concentration (FiO2), its use in determining the prognosis of acute pulmonary embolism (APE) was investigated.

METHODS AND RESULTS

This study retrospectively assessed 202 consecutive patients with APE confirmed by computed tomography or high probability lung scintigraphy. All patients underwent initial arterial blood gas analysis during the first 24 h of admission. Receiver-operating characteristic analyses were performed to determine the a/APO2 cut-off value for predicting 30-day death or 30-day composite events. Cut-off values for a/APO2 were used to determine stability in all patients and 2 subgroups (0.49 for all patients; 0.49 for FiO2 =0.21; 0.46 for FiO2 >0.21). Using the cut-off value of a/APO2 <0.49 for predicting 30-day death, the negative predictive value (NPV) was 90%, and the positive predictive value (PPV) was 30.3%. For the 30-day composite end point, the NPV was 81.3%, and the PPV was 40.9%. Excluding massive APE, the a/APO2 also had high NPV and moderate PPV in predicting short-term prognosis. This study additionally demonstrated a linear relationship between platelet count and a/APO2.

CONCLUSIONS

The cut-off value of a/APO2 <0.49 exhibits stability at variable FiO2 values and is a useful prognostic predictor in APE.

Prognostic Role of Alveolar-Arterial Oxygen Pressure Difference in Acute Pulmonary Embolism

BACKGROUND

This study investigated the utility of the alveolar - arterial oxygen pressure difference (AaDO (2)) in predicting the short-term prognosis of acute pulmonary embolism (PE).

METHODS AND RESULTS

This study retrospectively enrolled 114 consecutive patients with acute PE, diagnosed by either spiral computed tomography or high probability ventilation - perfusion lung scans. During the first 24 h of admission, all patients had initial artery blood gas collected under room air. Patient exclusion criteria were chronic lung disease, septic emboli, and moderate and low probability lung scans. Patients were assigned to 2 groups based on either 30-day death or a 30-day composite event. Receiver operating characteristic analyses was used to determine the AaDO(2) cut-off value for predicting primary and composite endpoints. Statistical analysis demonstrated significant differences in AaDO(2) between the 30-day composite endpoint group and the 30-day composite event-free survival group (p=0.012). The AaDO(2) had a strong trend between the 30-day death group and the survival group (p=0.062). The best cut-off value for AaDO(2) was 53 mmHg and using this, the positive predictive value for 30-day death was 25% and the negative predictive value was 92%. For the 30-day composite endpoint, the positive predictive value for AaDO(2) was 35%, and the negative predictive value was 84%. In this study, thrombocytopenia was also an indicator of poor prognosis for patients with acute PE.

CONCLUSION

The AaDO(2) measurement is a highly useful and simple measurement for predicting short-term prognosis in patients with acute PE. It has high negative predictive value and moderate positive predictive value for 30-day death and 30-day composite event. Aggressive thrombolytic treatment strategies should be considered for patients with an initial poor prognostic parameter (ie, AaDO(2) >or=53 mmHg).

Surgical treatment for chronic thromboembolic pulmonary hypertension under profound hypothermia and circulatory arrest in 24 patients

BACKGROUND

Chronic thromboembolic pulmonary hypertension (CTEPH) is a serious disease that induces hypoxemia and pulmonary hypertension, eventually leading to respiratory failure and right heart failure. We evaluated the results of surgical treatment in patients undergoing circulatory arrest under profound hypothermia.

METHODS

Between February 1995 and June 1999, 24 cases of CTEPH were surgically treated. The age of patients (11 males and 13 females) ranged from 21 to 71 years (mean 49+/-15 years). Because of hypoxemia, severe pulmonary hypertension (mean pulmonary artery pressure 45+/-7 mmHg ), and low cardiac output, the functional class of these patients was New York Heart Association (NYHA) III or IV. Following a median sternotomy, profound hypothermia was induced using cardiopulmonary bypass, and pulmonary thromboendarterectomy in the bilateral pulmonary arteries was performed under intermittent circulatory arrest. Surgery was performed emergently in four patients.

RESULTS

Of these 24 patients, 2 of 20 patients who underwent elective surgery and 3 of 4 patients who underwent emergent surgery died in the hospital. Symptoms of CTEPH markedly improved in 18 patients who survived the surgery. Pulmonary arterial pressure was decreased to 16+/-6 mmHg, and cardiac output was increased.

CONCLUSIONS

When CTEPH is resistant to medical treatment, surgical treatment is useful. When surgical indications are carefully selected, pulmonary thromboendarterectomy using intermittent circulatory arrest under profound hypothermia is quite effective for treating CTEPH.

Clinical importance of AaDO2 and pulmonary artery pressure as predicted by pulsed Doppler echocardiography at bedside in diagnosing pulmonary embolism

The authors evaluated clinical importance of alveolar-arterial PO2 difference (AaDO2) and pulmonary artery pressure (PAP) estimated by pulsed Doppler echocardiography in 31 patients with pulmonary embolism (PE). Echocardiographic estimates from flow velocity patterns in the right ventricular outflow tract showed significant correlation with actual measurements obtained by right cardiac catheterization. Furthermore, PAP as obtained by pulsed echocardiography was significantly higher in acute massive and recurrent multiple groups in comparison with the acute submassive group. AaDO2 was greatest in the acute massive group, followed by the recurrent multiple group, and then by the acute submassive group. These results suggest that analyses of AaDO2 and the echocardiographic estimation of PAP at bedside are successful in the diagnosis and classification of PE.