Cardiac tamponade after pulmonary endarterectomy: mind the left side…

Is pulmonary hypertension protective against cardiac tamponade? A systematic review

The presence of pulmonary hypertension (PH) may affect whether cardiac tamponade physiology develops from a pericardial effusion. Specifically, the increased intracardiac pressure and right ventricular hypertrophy associated with PH would seemingly increase the intrapericardial pressure threshold at which the right-sided chambers collapse. In this systematic review, we examined the impact of PH on the incidence, in-hospital and long-term mortality, and echocardiographic findings of patients with cardiac tamponade. Using the PRISMA guideline, a systematic search was conducted in PubMed, Academic Search Premier, Web of Science, Google Scholar, and the Cochrane Database for studies investigating PH and cardiac tamponade. The Newcastle-Ottawa Scale was used to analyze the quality of returned studies. Primary outcomes included the incidence of cardiac tamponade, as well as in-hospital and long-term mortality rates. Secondary outcomes were the presence or absence of echocardiographic findings of cardiac tamponade in patients with PH. Forty-three studies (9 cohort studies and 34 case reports) with 1054 patients were included. The incidence of cardiac tamponade was significantly higher in patients with PH compared to those without PH, 2.0% (95% CI 1.2-3.2%) vs. 0.05% (95% CI 0.05-0.05%), p < 0.0001, OR 40.76 (95% CI 24.8-66.9). The incidence of tamponade in patients with a known pericardial effusion was similar in those with and without PH, 20.3% (95% CI 12.0-32.3%) and 20.9% (95% CI 18.0-24.1%), p = 0.9267, OR 0.97 (95% CI 0.50-1.87). In patients with tamponade, those with PH demonstrated a significantly higher in-hospital mortality than those without PH, 38.8% (95% CI 26.4-52.8%) vs. 14.4% (95% CI 14.2-14.6%), p < 0.0001, OR 3.77 (95% CI 2.12-6.70). Long-term mortality in patients with tamponade was significantly lower in those with PH than in those without PH, 45.5% (95% CI 33.0-58.5%) vs. 59.1% (95% CI 54.7-63.4%), p = 0.0258, OR 0.576 (95% CI 0.33-1.01). However, after stratifying by non-malignant etiologies, the long-term mortality benefit for those with PH disappeared. In the studies that described specific echocardiographic findings of cardiac tamponade, only 10.5% of patients with PH and tamponade showed right atrial and right ventricular collapse. When evaluating patients with pericardial effusions, physicians must recognize the effects of underlying PH on the incidence, in-hospital and long-term mortality rates, and potentially atypical echocardiographic presentation of cardiac tamponade.

When is tamponade not an echocardiographic diagnosis… Or is it ever?

Although cardiac tamponade remains a clinical diagnosis, echocardiography is an essential tool to detect fluid in the pericardial space. Interpretation of echocardiographic findings and assessment of physiologic and hemodynamic consequences of a pericardial effusion require a thorough understanding of pathophysiologic processes. Certain echocardiographic signs point toward the presence of cardiac tamponade: a dilated inferior vena cava (IVC), collapse of the cardiac chambers, an inspiratory bulge of the interventricular septum into the left ventricle (LV) (the "septal bounce"), and characteristic respiratory variations of Doppler flow velocity recordings. However, in certain circumstances (e.g., mechanical ventilation, post-surgical patients, and pulmonary hypertension), these echocardiographic signs can be missing, despite the presence of clinical tamponade. Failure to recognize a potentially life-threatening clinical condition due to the absence of corresponding echocardiographic findings can delay both diagnosis and life-saving treatment. Thus, in the context of critical care, echocardiography should only be used to confirm the presence of pericardial fluid or localized hematoma, and the diagnosis of tamponade should rely on clinical criteria.

Pseudo Heparin Resistance After Pulmonary Endarterectomy: Role of Thrombus Production of Factor VIII

Pulmonary endarterectomy (PEA) is the main treatment for chronic thromboembolic pulmonary hypertension (CTEPH). Postoperative unfractionated heparin dosing can be monitored by activated partial thromboplastin time (APTT) or by anti-factor Xa activity (anti-Xa). In pseudo heparin resistance, APTT response to heparin is blunted due to elevated Factor VIII (FVIII) which can underestimate anticoagulation. We examined possible pseudo heparin resistance after PEA and assessed the impact of FVIII. APTT response to heparin before and after operation was determined in 13 PEA patients anticoagulated with unfractionated heparin. APTT and anti-Xa concordance was analyzed from paired postoperative samples, and antithrombin, fibrinogen and FVIII levels were measured. Single-cell RNA sequencing was used to characterize FVIII gene expression in PEA specimens of 5 patients. APTT response to heparin was blunted after PEA. APTT and anti-Xa were discordant in 36% of postoperative samples and most common discordant patterns were subtherapeutic APTT with therapeutic (16%) or supratherapeutic (11%) anti-Xa. Overall, APTT underestimated anticoagulation relative to anti-Xa in one-third of the samples. FVIII levels were elevated before surgery, increased substantially 1 and 3 days (median 4.32 IU/mL) after PEA, and were higher in discordant than concordant samples. Single-cell RNA sequencing showed FVIII gene expression in PEA specimen endothelial cells. Pseudo heparin resistance is common after PEA likely due to highly elevated postoperative FVIII levels indicating that anti-Xa reflects postoperative heparinization better than APTT in these patients. FVIII production by the pulmonary artery endothelium may participate in local prothrombotic processes important for CTEPH pathogenesis.