Infectious Diseases of the Heart: Pathophysiology, Clinical and Imaging Overview.

Myriad infectious organisms can infect the endocardium, myocardium, and pericardium, including bacteria, fungi, parasites, and viruses. Significant cardiac infections are rare in the general population but are associated with high morbidity and mortality as well as increased risk in certain populations, such as the elderly, those undergoing cardiac instrumentation, and intravenous drug abusers. Diagnostic imaging of cardiac infections plays an important role despite its variable sensitivity and specificity, which are due in part to the nonspecific manifestations of the central inflammatory process of infection and the time of onset with respect to the time of imaging. The primary imaging modality remains echocardiography. However, cardiac computed tomography and magnetic resonance (MR) imaging have emerged as the modalities of choice wherever available, especially for diagnosis of complex infectious complications including abscesses, infected prosthetic material, central lines and instruments, and the cryptic manifestations of viral and parasitic diseases. MR imaging can provide functional, morphologic, and prognostic value in a single examination by allowing characterization of inflammatory changes from the acute to chronic stages, including edema and the patterns and extent of delayed gadolinium enhancement. We review the heterogeneous and diverse group of cardiac infections based on their site of primary cardiac involvement with emphasis on their cross-sectional imaging manifestations. Online supplemental material is available for this article. (©)RSNA, 2016.

Admittance to detect alterations in left ventricular stroke volume.

BACKGROUND: Implantable cardioverter-defibrillators monitor intracardiac electrograms (EGMs) to discriminate between ventricular and supraventricular tachycardias. The incidence of inappropriate shocks remains high because of misclassification of the tachycardia in an otherwise hemodynamically stable individual. Coupling EGMs with an assessment of left ventricular (LV) stroke volume (SV) could help in gauging hemodynamics during an arrhythmia and reducing inappropriate shocks. OBJECTIVE: The purpose of this study was to use the admittance method to accurately derive LV SV. METHODS: Ultrasonic flow probe and LV endocardial crystals were used in canines (n = 12) as the standard for LV SV. Biventricular pacing leads were inserted to obtain admittance measurements. A tetrapolar, complex impedance measurement was made between the Bi-V leads. The real and imaginary components of impedance were used to discard the myocardial component from the blood component to derive instantaneous blood conductance (Gb). Alterations in SV were measured during right ventricular pacing, dopamine infusion, and inferior vena cava occlusion. RESULTS: Gb tracks steady-state changes in SV more accurately than traditional magnitude (ie, |Y|, without removal of the muscle signal) during right ventricular pacing and dopamine infusion (P = .004). Instantaneous LV volume also was tracked more accurately by Gb than ∣Y∣ in the subset of subjects that underwent inferior vena cava occlusions (n = 5, P = .025). Finite element modeling demonstrates that admittance shifts more sensitivity of the measurement to the LV blood chamber as the mechanism for improvement (see Online Appendix). CONCLUSION: Monitoring LV SV is possible using the admittance method with biventricular pacing leads. The technique could be piggybacked to complement EGMs to determine if arrhythmias are hemodynamically unstable.

Imaging patients with cardiac trauma.

In the United States, trauma is the leading cause of death among those who are 1-44 years old, with cardiovascular injuries representing the second most common cause of traumatic death after central nervous system injuries. Evaluation of trauma patients with suspected cardiac injury may be complex and include electrocardiography, measurement of cardiac biomarkers, and imaging examinations. Contrast material-enhanced computed tomography (CT) has become one of the most valuable imaging tools available for evaluating hemodynamically stable patients with suspected cardiac injury. The presence of hemopericardium, with or without cardiac tamponade, is one of the most significant findings of cardiac injury. Other complications that result from blunt cardiac injury, such as pericardial rupture and cardiac herniation, may be readily depicted at multidetector CT. Assessment of patients with cardiac injuries, particularly those with penetrating injuries, is a challenging and time-critical matter, with clinical and imaging findings having complementary roles in the formation of an accurate diagnosis. Patients who are hemodynamically stable, particularly those with penetrating cardiac injuries, also may benefit from a timely imaging examination. In addition to chest radiography, other available modalities such as transthoracic and transesophageal echocardiography, nuclear medicine, and magnetic resonance imaging may play a role in selected cases.