Renato Prediletto

Value of transthoracic echocardiography in the diagnosis of pulmonary embolism: results of a prospective study in unselected patients

PURPOSE Echocardiography is advocated by some as a useful diagnostic test for patients with suspected pulmonary embolism (PE), but its diagnostic accuracy is unknown. The present study was undertaken to determine prospectively the sensitivity and specificity of transthoracic echocardiography in the diagnosis of PE. SUBJECTS AND METHODS We examined 110 consecutive patients with suspected PE. The study protocol included assessment of clinical probability, echocardiography, and perfusion lung scanning. Pulmonary angiography was performed in all patients with abnormal scans. As echocardiographic criteria to diagnose acute PE, we used the presence of any two of the following: right ventricular (RV) hypokinesis, RV end-diastolic diameter >27 mm (without RV wall hypertrophy), or tricuspid regurgitation velocity >2.7 m/sec. Clinical estimates of PE served as pretest probabilities in calculating, after echocardiography, the posttest probabilities of PE. RESULTS Pulmonary angiography confirmed PE in 43 (39%) of 110 patients. Echocardiographic diagnostic criteria for PE yielded a sensitivity of 56% and a specificity of 90%. For pretest probabilities of 10%, 50%, and 90%, the posttest probabilities of PE conditioned by a positive echocardiogram were 38%, 85%, and 98%, respectively. The posttest probabilities of PE conditioned by a negative echocardiogram were 5%, 33%, and 81%, respectively. CONCLUSIONS In unselected patients with suspected PE, transthoracic echocardiography fails to identify some 50% of patients with angiographically proven PE. Although echocardiographic findings of RV strain, paired with a high clinical likelihood, support a diagnosis of PE, the transthoracic echocardiography has to have a better sensitivity to be used as a screening test to rule out PE.

A diagnostic strategy for pulmonary embolism based on standardised pretest probability and perfusion lung scanning: a management study

Pulmonary embolism remains a challenging diagnostic problem. We developed a simple diagnostic strategy based on combination of assessment of the pretest probability with perfusion lung scan results to reduce the need for pulmonary angiography. We studied 390 consecutive patients (78% in-patients) with suspected pulmonary embolism. The pretest probability was rated low (<10%), intermediate (>10%, ≤50%), moderately high (>50%, ≤90%) or high (>90%) according to a structured clinical model. Perfusion lung scans were independently assigned to one of four categories: normal; near-normal; abnormal, suggestive of pulmonary embolism (wedge-shaped perfusion defects); abnormal, not suggestive of pulmonary embolism (perfusion defects other than wedge shaped). Pulmonary embolism was diagnosed in patients with abnormal scans suggestive of pulmonary embolism and moderately high or high pretest probability. Patients with normal or near-normal scans and those with abnormal scans not suggestive of pulmonary embolism and low pretest probability were deemed not to have pulmonary embolism. All other patients were allocated to pulmonary angiography. Patients in whom pulmonary embolism was excluded were left untreated. All patients were followed up for 1 year. Pulmonary embolism was diagnosed non-invasively in 132 patients (34%), and excluded in 191 (49%). Pulmonary angiography was required in 67 patients (17%). The prevalence of pulmonary embolism was 41% (n=160). Patients in whom pulmonary embolism was excluded had a thrombo-embolic risk of 0.4% (95% confidence interval: 0.0%–2.8%). Our strategy permitted a non-invasive diagnosis or exclusion of pulmonary embolism in 83% of the cases (95% confidence interval: 79%–86%), and appeared to be safe.

Inappropriateness of Cardiovascular Radiological Imaging Testing; A Tertiary Care Referral Center Study

Aims Radiological inappropriateness in medical imaging leads to loss of resources and accumulation of avoidable population cancer risk. Aim of the study was to audit the appropriateness rate of different cardiac radiological examinations. Methods and Principal Findings With a retrospective, observational study we reviewed clinical records of 818 consecutive patients (67±12 years, 75% males) admitted from January 1-May 31, 2010 to the National Research Council – Tuscany Region Gabriele Monasterio Foundation cardiology division. A total of 940 procedures were audited: 250 chest x-rays (CXR); 240 coronary computed tomographies (CCT); 250 coronary angiographies (CA); 200 percutaneous coronary interventions (PCI). For each test, indications were rated on the basis of guidelines class of recommendation and level of evidence: definitely appropriate (A, including class I, appropriate, and class IIa, probably appropriate), uncertain (U, class IIb, probably inappropriate), or inappropriate (I, class III, definitely inappropriate). Appropriateness was suboptimal for all tests: CXR (A = 48%, U = 10%, I = 42%); CCT (A = 58%, U = 24%, I = 18%); CA (A = 45%, U = 25%, I = 30%); PCI (A = 63%, U = 15%, I = 22%). Top reasons for inappropriateness were: routine on hospital admission (70% of inappropriate CXR); first line application in asymptomatic low-risk patients (42% of CCT) or in patients with unchanged clinical status post-revascularization (20% of CA); PCI in patients either asymptomatic or with miscellaneous symptoms and without inducible ischemia on non-invasive testing (36% of inappropriate PCI). Conclusion and Significance Public healthcare system – with universal access paid for with public money – is haemorrhaging significant resources and accumulating avoidable long-term cancer risk with inappropriate cardiovascular imaging prevention.

How Reliable Are Current Data for Assessing the Actual Prevalence of Chronic Obstructive Pulmonary Disease

Background Estimating COPD occurrence is perceived by the scientific community as a matter of increasing interest because of the worldwide diffusion of the disease. We aimed to estimate COPD prevalence by using administrative databases from a city in central Italy for 2002–2006, improving both the sensitivity and the reliability of the estimate. Methods Multiple sources were used, integrating the hospital discharge register (HDR), clinical charts, spirometry and the cause-specific mortality register (CMR) in a longitudinal algorithm, to reduce underestimation of COPD prevalence. Prevalence was also estimated on the basis of COPD cases confirmed through spirometry, to correct misclassification. Estimating such prevalence relied on using coefficients of validation, derived as the positive predictive value (PPV) for being an actual COPD case from clinical and spirometric data at the Institute of Clinical Physiology of the National Research Council. Results We found that sensitivity of COPD prevalence increased by 37%. The highest estimate (4.43 per 100 residents) was observed in the 5-year period, using a 3-year longitudinal approach and combined data from three sources. We found that 17% of COPD cases were misclassified. The above estimate of COPD prevalence decreased (3.66 per 100 residents) when coefficients of validation were applied. The PPV was 80% for the HDR, 82% for clinical diagnoses and 91% for the CMR. Conclusions Adjusting the COPD prevalence for both underestimation and misclassification of the cases makes administrative data more reliable for epidemiological purposes.

The assessment of gas exchange by automated analysis of O2 and CO2 alveolar to arterial differences

SummaryA computer program to measure breath by breath alveolar pressure (PA) and alveolar to arterial difference (AaD) for O2 and CO2, by a mass-spectrometer has been implemented. The program allows the determination of alveolar gas by different methods: 1. Bohrs equation (BE); 2. ideal alveolar air equation for O2 (IDO2); 3. end-tidal (ET); 4. by the Rahns definition of ‘mean alveolar gas’, i.e., alveolar pressures are defined when instantaneous respiratory exchange ratio (IRQ) equals mean respiratory exchange ratio (MRQ). This automated technique has been used in 16 patients with chronic obstructive lung disease (COLD) and 15 patients with pulmonary embolism (APE). In both groups of patients it was always possible to find in each breath the point where IRQ=MRQ and therefore to measure AaD by RD. IDO2 was significantly lower than PAO2 by the other methods. Also ET values of O2 and CO2 were significantly different from RD and BE in both groups of patients, however the difference was consistently higher in COLD patients. The different shape of the expirograms (steeper expirograms in COLD) is responsible for this different result. RD and BE AaD characterize gas exchange more precisely than ET, because the contribution of high VA/Q units is also evaluated. This is particularly important in COLD patients.Consideration on dead space measurements are also reported both for COLD and APE patients. In conclusion this automated technique provides the assessment of gas exchange for the use in clinical respiratory physiology and for the monitoring of gas-exchange in critically ill patients.

Routine Chest X-ray: Still Valuable for the Assessment of Left Ventricular Size and Function in the Era of Super Machines?

Objectives: The development of technologically advanced, expensive techniques has progressively reduced the value of chest X-ray in clinical practice for the assessment of left ventricular (LV) dilatation and dysfunction. Although controversial data are reported on the role of this widely available technique in cardiac assessment, it is known that the cardio-thoracic ratio is predictive of risk of progression in the NYHA Class, hospitalization, and outcome in patients with LV dysfunction. This study aimed to evaluate the reliability of the transverse diameter of heart shadow [TDH] by chest X-ray for detecting LV dilatation and dysfunction as compared to Magnetic Resonance Imaging (MRI) performed for different clinical reasons. Materials and Methods: In 101 patients, TDH was measured in digital chest X-ray and LV volumes and ejection fraction (EF) by MRI, both exams performed within 2 days. Results: A direct correlation between TDH and end-diastolic volumes (r = .75, P<0.0001) was reported. TDH cut-off values of 14.5 mm in females identified LV end-diastolic volumes >150 mL (sensitivity: 82%, specificity: 69%); in males a cut-off value of 15.5 mm identified LV end-diastolic volumes >210 mL (sensitivity: 84%; specificity: 72%). A negative relation was found between TDH and LVEF (r = -.54, P<0.0001). The above cut-off values of TDH discriminated patients with LV systolic dysfunction – LVEF <35% (sensitivity and specificity: 67% and 57% in females; 76% and 59% in males, respectively). Conclusions: Chest X-ray may still be considered a reliable technique in predicting LV dilatation by the accurate measurement of TDH as compared to cardiac MRI. Technologically advanced, expensive, and less available imaging techniques should be performed on the basis of sound clinical requests.

Non-invasive diagnosis of pulmonary embolism

Pulmonary embolism (PE) remains a challenging diagnostic problem because it mimics other cardiopulmonary disorders. Pulmonary angiography is still the reference standard for diagnosing PE but it is costly, invasive and not readily available. Non-invasive diagnostic strategies have therefore been developed to forego pulmonary angiography in patients suspected of having PE. Ventilation/perfusion lung scanning is, at present, the most widely used non-invasive diagnostic test for PE. A high probability ventilation/perfusion scan (segmental or greater perfusion defects with normal ventilation) warrants the institution of anticoagulant therapy especially when paired with high clinical suspicion of PE. Yet, only a minority of patients with confirmed PE have high probability ventilation/perfusion scans. Ventilation/perfusion abnormalities other than those of the high probability scan should be regarded as non-diagnostic. Under these circumstances, documentation of deep vein thrombosis by non-invasive leg testing warrants anticoagulation without the need for angiography. However, a single negative venous study result does not permit to rule out PE in patients with non-diagnostic ventilation/perfusion scans. Results of a recent prospective study indicate that accurate diagnosis or exclusion of PE is possible with perfusion lung scanning alone (without ventilation imaging). Combining perfusion lung scanning with clinical assessment helps to restrict the need for angiography to a minority of patients with suspected PE.

Ventilation-perfusion heterogeneity and gas exchange variables in acute pulmonary embolism evaluated by two different computerized techniques

SummaryThe mechanisms by which the disturbances of gas exchange develop in human pulmonary embolism are unknown. We investigated whether the inequality of ventilation-perfusion ratio is associated with the abnormalities of pulmonary gas exchange as evaluated by two different computerized techniques. We measured the alveolar to arterial gradients of oxygen and carbon dioxide by means of a computer based system with a mass spectrometer and the ventilation-perfusion distributions by the multiple inert gas technique in 5 patients with acute pulmonary embolism. In these subjects there was a marked ventilation-perfusion inhomogeneity, as detected from inert gases and this finding was in agreement with the impairment of the alveolar to arterial gradients and of their derived indexes. Consideration on the responsible mechanisms for the disturbances of gas exchange are also reported. In conclusion these two computerized techniques provide a useful assessment of the ventilation-perfusion relationships in order to explain the disturbances of gas exchange in critically ill patients.