Thomas R. Gehrig

Low-molecular-weight heparin for thromboprophylaxis in pregnant women with mechanical heart valves.

Background. Pregnancy in a woman with a mechanical heart valve is a life-threatening situation. Due to the inability of unfractionated heparin to prevent valvular thromboses, warfarin or other vitamin K antagonists have been the preferred anticoagulants for the mother. They are, however, potentially harmful to the fetus. With the advent of low-molecular-weight heparins, clinicians were hopeful for an alternative that was safe for the fetus, but more effective than unfractionated heparin, which carries a 29–33% risk of life-threatening thromboses and a 7–15% chance of mortality. Unfortunately, fatal thromboses have occurred with low-molecular-weight heparin as well. Methods. We searched the MEDLINE database and other sources to identify cases of the use of low-molecular-weight heparin for thromboprophylaxis in women with mechanical heart valves. Results. We found 73 cases and added three of our own for a total of 76. There were 17 thrombotic events (22%). Thirteen were valve thromboses, two were strokes, and two were myocardial infarctions. There were three deaths (4%). Conclusions. While pregnant women with mechanical heart valves who receive low-molecular-weight heparin for thromboprophylaxis are at extremely high risk of life-threatening thromboses, there is no evidence that low-molecular-weight heparin is inferior to unfractionated heparin.

Thrombolytic Therapy for Thrombosis of Continuous Flow Ventricular Assist Devices

BACKGROUND Despite chronic systemic anticoagulation, advanced heart failure patients treated with a continuous-flow left ventricular assist device (LVAD) remain at risk for pump thrombosis. Pump thrombosis may initially be suspected in the setting of clinical and biochemical evidence for intravascular hemolysis, putatively related to shear stress on red blood cells propelled through a partially occluded pump. Limited data exist to guide management in these patients. METHODS AND RESULTS We present a series of 8 LVAD patients who presented with intravascular hemolysis secondary to pump thrombosis who were treated with intraventricular thrombolytic therapy. In 3 patients, thrombolytic therapy led to complete and lasting resolution of hemolysis, suggesting successful dissolution of pump thrombus. In the remaining 5 patients, thrombolytic therapy ultimately failed to halt or reverse pump thrombosis and hemolysis: 1 patient required emergent pump exchange, 2 patients progressed to cardiogenic shock and died, 1 patient suffered a debilitating stroke after which care was withdrawn, and 1 patient underwent cardiac transplantation. CONCLUSIONS In the setting of LVAD thrombosis, thrombolytic therapy is an alternate treatment strategy in a subset of patients. Candidacy for this alternate procedure must carefully weigh the risks of complications, including hemorrhage and thromboembolism.

Cholesterol emboli after invasive cardiac procedures.

“Atheromatous emboli” is a general description for embolization of any atheromatous material. The term “atheroemboli” is used to refer to the dislodgement of vascular plaque material that contains cholesterol crystals plus red blood cells and fibrin. These can occlude major systemic vessels

Cataloguing the geometry of the human coronary arteries: A potential tool for predicting risk of coronary artery disease

BACKGROUND The non-uniform distribution of atherosclerosis in the human vasculature suggests that local fluid dynamics or wall mechanics may be involved in atherogenesis. Thus certain aspects of vascular geometry, which mediates both fluid dynamics and wall mechanics, might be risk factors for coronary atherosclerosis. Cataloguing the geometry of normal human coronary arteries and its variability is a first step toward identifying specific geometric features that increase vascular susceptibility to the disease. METHODS Images of angiographically normal coronary arteries, including 32 left anterior descending (LAD) and 35 right coronary arteries (RCA), were acquired by clinical biplane cineangiography from 52 patients. The vessel axes in end diastole were reconstructed and geometric parameters that included measures of curvature, torsion and tortuosity were quantified for the proximal, middle and distal segments of the arteries. RESULTS Statistical analysis shows that (1) in the LAD, curvature, torsion and tortuosity are generally highest in the distal portion, (2) in the RCA, these parameters are smallest in the middle segment, (3) the LAD exhibits significant higher torsion than the RCA (P < 0.005), and (4) >80% of the variability of coronary arterial geometry can be expressed in terms of two factors, one dominated by the curvature measures and tortuosity, and the other emphasizing the torsion parameters. CONCLUSIONS This study has comprehensively documented the normal arterial geometry of the LAD and RCA in end diastole. This information may be used to guide the identification of geometric features that might be atherogenic risk factors.

Comparison of coronary artery dynamics pre- and post-stenting

Stents have dramatically improved the treatment of coronary artery disease. Since the implantation of stents changes the geometry and dynamics of the coronary artery, it is reasonable to hypothesize that some of these changes may have an important effect on the development of atherosclerosis by modulating the mechanical environment. In this paper, we presented a method to compare the geometric dynamics of the coronary artery before and after stenting using biplane angiography. Two cases are reviewed and a number of parameters are proposed to describe the longitudinal change of the vessel before and after stenting. This analysis technique has the potential to identify some aspects of stent design and procedure that might improve the success rate with this therapeutic approach.

Measurement of the transverse strain tensor in the coronary arterial wall from clinical intravascular ultrasound images

Atherosclerotic plaque rupture is the major cause of acute coronary syndromes. Currently, there is no reliable diagnostic tool to predict plaque rupture. Knowledge of plaque mechanical properties based on local artery wall strain measurements would be useful for characterizing its composition and predicting its vulnerability. Due to cardiac motion, strain estimation in clinical intravascular ultrasound (IVUS) images is extremely challenging. A method is presented to estimate cross-sectional coronary artery wall strain in response to cardiac pulsatile pressure using clinically acquired IVUS images, which are acquired in continuous pullback mode. First, cardiac phase information is retrieved retrospectively from an IVUS image sequence using an image-based gating method, and image sub-sequences at systole and diastole are extracted. Then, images at branch sites are used as landmarks to align the two image sub-sequences. Finally, the paired images at each site are registered to measure the 2D strain tensor of the coronary artery cross-section. This method has been successfully applied to IVUS images of a left anterior descending (LAD) coronary artery acquired clinically during a standard procedure. Such complete strain information should be useful for identifying vulnerable plaque.

The VB‐1 catheter: An improved catheter for difficult‐to‐engage internal mammary artery grafts

As patients with prior coronary artery bypass grafting age, internal mammary artery grafts are more frequently encountered in the cardiac catheterization laboratory. Angiography and interventions involving these grafts are often difficult, particularly in patients with tortuous subclavian anatomy and/or proximal internal mammary artery origins. We describe a new catheter shape, the Cordis Behar Internal Mammary, VB‐1, which allows selective intubations of both right and left internal mammary arteries that are not possible with conventional catheters. Cathet Cardiovasc Intervent 2003;59:361–365.

Ascending aorta to main pulmonary artery fistula following orthotopic heart transplantation: successful percutaneous closure employing an Amplatzer Duct Occluder.

A 60-year-old man with end-stage heart failure underwent orthotopic heart transplantation. Before transplantation, he had elevated pulmonary artery (PA) pressures (60/17 mm Hg, mean PA 35 mm Hg) and pulmonary vascular resistance (PVR) (6.6 Wood units). Following transplantation, he initially did

Post-operative Care of the Patient Undergoing Valve Surgery

There are few naturally occurring medical illnesses that rival the acuity and severity of illness which can complicate the post-operative course following cardiac valvular surgery. Some complications are potentially predictable, while others are not. Fortunately, improved surgical and anesthetic techniques have decreased the frequency of many of these adverse events. Cardiologists may receive little training with respect to post-operative evaluation and management of patients following valvular heart surgery. Nevertheless, they are asked to provide guidance to patients considering such surgery and are asked to assist in the management of individuals when complications do arise. Understanding the risks of valvular surgery is important in guiding the patient pre-operatively and in assisting in their post-operative recovery. The purpose of this chapter is to discuss the post-operative cardiac and extra-cardiac complications frequently encountered following cardiac surgery.

ESTIMATION OF CORONARY ARTERIAL WALL STRAIN IN CLINICAL IVUS IMAGES

In this study, we propose a practical method to estimate cross-sectional wall strain distribution of coronary arteries from clinically acquired intravascular ultrasound (IVUS) images in continuous pullback mode. First, cardiac phase information is retrieved retrospectively from an IVUS image sequence using an image-based gating method, and image sub-sequences at systole and diastole are extracted. Images at branch sites are used as benchmarks to align the two image sub-sequences. Finally, the paired images at each site are registered to estimate the cross-sectional strain of the coronary artery.