Penetrating cardiac injuries

Penetrating cardiac injuries pose a tremendous challenge to any trauma surgeon. Time, sound judgment, aggressive intervention, and surgical technique are the most important factors contributing to positive outcomes. This article extensively reviews the history, surgical management, and techniques needed to deal with these critical injuries. This year commemorates the one hundredth anniversary of the first successful repair of a cardiac injury.

Acute tamponade alters subendo- and subepicardial pressure-flow relations differently during vasodilation

Instantaneous diastolic left coronary artery pressure-flow relations (PFR) shift during acute tamponade as pressure surrounding the heart increases. Coronary pressure at zero flow (Pf = 0) on the linear portion of the PFR is the weighted mean of the different myocardial waterfall pressures, the distribution of which varies across the left ventricular wall during diastole. However, instantaneous PFR measured in large epicardial coronary arteries cannot be used to estimate Pf = 0 in the different myocardial tissue layers. During coronary vasodilatation in a capacitance-free model, myocardial PFR differs from subendocardium to subepicardium. Therefore, we studied the effects of acute tamponade during maximal pharmacology induced coronary vasodilatation on myocardial PFR in in situ anesthetized dogs. Tamponade reduced cardiac output, aortic pressure, and coronary blood flow. Results demonstrate that different mechanisms influence distribution of myocardial blood flow during tamponade. Subepicardial vascular resistance is unchanged and the extrapolated Pf = 0 is increased, thereby shifting PFR to a higher intercept on the pressure axis. Subendocardial vascular resistance is increased while the extrapolated Pf = 0 remains unchanged. Results indicate that in the setting of acute tamponade with coronary vasodilatation different mechanisms regulate the distribution of myocardial blood flow: in the subepicardium only outflow pressure increases, whereas in the subendocardium only vascular resistance increases.

Pericardial actinomycosis: case report and review

Pericardial actinomycosis is rare and frequently goes unrecognized during life, a circumstance due in part to a paucity of clinical manifestations and to a low rate of positivity in cultures. We present a case report of pericardial actinomycosis and a review of 18 other cases reported in the literature since 1950. Possible risk factors include aspiration pneumonia, alcohol abuse, and periodontal disease. Actinomyces may cause purulent pericarditis that evolves into cardiac tamponade or constrictive pericarditis. Clues to the identity of the causative organism (e.g., draining sinus tracts and the presence of sulfur granules) are frequently absent, and cultures often fail to yield the organism. Histologic examination of material obtained by biopsy is often necessary to make the diagnosis. Most cases originate from a thoracopulmonary site of actinomycosis and spread directly to the pericardium. Widespread dissemination to extrathoracic organs is uncommon. Treatment consists of high-dose, long-term antimicrobial therapy as well as drainage of the pericardial space.

Arteriovenous acid-base disparity in circulatory failure: studies on mechanism

The normal relationship between arterial and venous acid-base composition is altered in hemodynamic compromise. Because the mechanism of this phenomenon remains conjectural, we have studied the acid-base profile and the end-tidal PCO2 of dogs with normal or depressed hemodynamic status in association with either normal ventilation or respiratory arrest. Reductions in cardiac output widened the arteriovenous difference in PCO2 and pH, largely due to arterial hypocapnia but also to venous hypercapnia, and decreased end-tidal PCO2. The arteriovenous gradients for PCO2 and pH of -5.1 +/- 0.4 mmHg and 0.02 +/- 0.01, respectively, during normal hemodynamics widened progressively with graded circulatory compromise reaching values of -30 +/- 5 mmHg for PCO2 (P less than 0.01) and 0.35 +/- 0.05 for pH (P less than 0.01) during cardiac arrest. Development of this disparity, however, required the presence of substantial pulmonary ventilation, since respiratory arrest obliterated the arteriovenous gradients. We propose that arterial hypocapnia, which occurs in association with reduced CO2 excretion, is secondary to an increased ventilation-to-perfusion ratio that reflects a disproportionate decrement in cardiac output. Venous hypercapnia, on the other hand, results from a greater than normal addition of CO2 per unit of blood traversing the capillaries of the hypoperfused peripheral tissues and a diminished CO2 excretion because of pulmonary hypoperfusion. Titration of bicarbonate stores by ongoing production of organic acids might also contribute to venous hypercapnia.

Cardiac tamponade as a presentation of malignant thymoma

Morphologic, cytochemical and immunocytochemical studies of pericardial fluid from a 30-year-old man presenting with cardiac tamponade are described. Based on the results of the immunocytochemical studies and the histologic examination of excised pericardium, a diagnosis of malignant thymoma was made. This is the first documented case in which malignant cells were found in the pericardial effusion in a patient with invasive thymoma. The significance of using a multidisciplinary approach to the study of body fluids is discussed.

Induction of controlled cardiac tamponade in the management of massive unexplained postcardiotomy bleeding. Case report and review of the literature

Massive unexplained bleeding is a catastrophic complication of open heart surgery. The following paper describes a successful attempt to terminate such a hemorrhage by induction of controlled cardiac tamponade which caused augmentation of mediastinal pressure without hemodynamic decompensation, thereby aiding in hemostasis. This modality has not previously reported. Few events in clinical medicine are so ominous as the major unexplained hemorrhage. Diffuse bleeding from multiple transected small vessels may be controlled by mechanical techniques which apply pressure directly over the bleeding area. However, where the mediastinum is the source of bleeding, application of such a direct pressure with a closed chest, is both technically difficult and potentially risky. Reported attempts to stop bleeding by increasing the mediastinal pressure included the induction of pneumothorax, and the increase of positive end expiratory pressure (PEEP) has been published. To the best of our knowledge, a deliberate induction of controlled cardiac tamponade in order to terminate prolonged unexplained massive postcardiotomy hemorrhage has not been reported so far.

Inhibition of peripheral vascular compensation after the induction of myocardial ischemia in dogs

The fact that peripheral vascular resistance fails to increase, or does so to only a small degree, thus contributing to hypotension after the onset of myocardial ischemia, has been noted in both clinical and experimental studies. We examined this phenomenon in canine kidney, mesentery, spleen, and skeletal muscle after occlusion via ligation of the circumflex coronary artery. Animals anesthetized with pentobarbital sodium (30 mg/kg, IV) and with intact vagus nerves exhibited reduced cardiac output (CO), maintenance of mean arterial blood pressure (MAP) at or near control levels, and increased total peripheral resistance (TPR). Blood flows to the kidney (RBF) and mesentery (MBF) were decreased resulting in substantial elevations of renal vascular resistance (RVR) and mesenteric vascular resistance (MVR). Blood flow supplied to the hindlimb skeletal muscle (FBF) by the femoral artery did not vary substantially from control levels and, therefore, neither did femoral vascular resistance (FVR). Splenic arterial blood flow (SpBF) was somewhat decreased but splenic vascular resistance (Sp VR) remained un changed. Heart rate exhibited no change from control levels.

When coronary artery ligation was preceded by bilateral cervical vagot omy, CO was decreased as before but MAP exhibited sustained decreases. No change from control values was noted in RBF, FBF, MBF, or SpBF. RVR, MVR, and Sp VR were significantly decreased while FVR remained unchanged. TPR in all cases was increased but not to the same degree as was noted in nonvagotomized animals. Again, no change in heart rate occurred.

Unlike the hemodynamic pattern observed in vagotomized dogs subjectedto the induction of myocardial ischemia, treatment of animals with a cholinergic blocking dose of atropine sulfate (1 mg/kg, IV) before coronary artery occlusion produced maintenance of MAP at or near control levels, lesser and slower reductions of CO and significantly increased TPR. No change was observed in RBF, FBF, MBF, SpBF or in RVR, FVR, MVR, and SpVR. Although there were no changes in heart rate from control levels, these values in atropinized dogs were usually higher than corresponding figures in other series.

When the induction of mild pericardial tamponade was substituted for coronary artery ligation, both vagotomized and non-vagotomized dogs exhibited normal peripheral compensations to the resulting hypotension and CO reduction, i.e., RBF decreased markedly and RVR was substantially increased as was TPR. No change in heart rate occurred.

These results indicate that (1) myocardial ischemia is necessary to trigger the abnormal loss of peripheral vascular compensatory responses; (2) vagal afferent nerves serve a protective function by mediating normal compensatory maneuvers, and (3) an additional mechanism, activated by ischemia but masked by the vagi, may cause inappropriate vasodilation when vagal afferent nerve activity is lost. A model has been constructed that presents a possible mechanism mediating the described phenomena.

[The relevance of spontaneous ruptures of the aorta in forensic medicine (author's transl)]

Report on 42 cases of "spontaneous rupture of the aorta" (0.4% of the examined autopsies in the case of 9817 court-ordered post mortem examinations, or 1.4% of the deaths by "natural causes"). The ratio of sexes male to female was 2:1. The cause of changes in blood vessels were arteriosclerosis (53.6%) and medionecrosis (31.7%). In 57.1% of cases, ruptures were in the ascending part, in 11.9% in the arch, in 7.1% in the thoracic descending part and in 21.4% in the abdominal descending part. With the exception of 3 cases with incomplete rupture and death due to circulation failure, the commonest causes of death were pericardial tamponade or hemorrhage into the thoracic or abdominal cavity. In 6 cases (1 X arteriosclerosis, 5 X medionecrosis) the question had to be examined as to whether external influences were only an initiating factor or whether they constituted a legally relevant cause for the rupture and subsequent death. In 4 cases such a relationship was ruled out after examination of the circumstances and autopsy findings. In 2 cases (cases 3 and 4) the role of an external influence could not be ruled out for the moment. The penal and insurance problems are discussed in depth on the basis of the literature.

Surgical treatment of aneurysms of the ascending aorta. With special reference to cystic medial necrosis of the aorta

The clinical series comprised 14 patients with aneurysms of the ascending aorta. In the autopsy series, there were additionally 19 patients, who had died suddenly as a results of free perforation or dissection of the ascending aorta. In the clinical series, the cause of the aneurysmal formation was cystic medial necrosis in 10 patients, 8 of whom had severe aortic valve insufficiency. Twelve patients were operated on using extracorporeal circulation, Both the ascending aorta and aortic valve were replaced with prosthesis in 6 cases. Three patients underwent emergency surgery due to pericardial tamponade. All three died, despite a technically successful operation. One patient out of 9 electively operated upon died. A follow-up examination was carried out on the 5 surviving cystic medial necrosis patients. Aneurysms of the sinuses of Valsalva developed after supracoronary resection in 2 patients. The results showed that elective operations in the event of aneurysms of the ascending aorta can be carried out with an acceptably low mortality rate. However, after supracoronary resection, in cases of cystic medial necrosis, the risk of developing aneurysms of the proximal aortic remnant seems obvious. Therefore, in patients in whom the whole aortic root is involved, total removal of the ascending aorta and re-implantation of the coronary ostia into the prosthetic tube is preferable.

Atrial receptors and renal function

The hypothesis that receptors in the heart or pulmonary vasculature initiate a reflex that influences urine flow was derived from experiments designed to evaluate the effect of mechanical ventilation on renal function. These experiments indicated that urine flow usually decreases during positive-pressure breathing and usually increases during negative-pressure breathing. It was surmised that impulses from certain cardiopulmonary receptors affect the secretion of ADH, which in turn influences urine flow. A subsequent investigation appeared to localize the pertinent receptors to the left atrium, but the results of this particular investigation were influenced by several complication factors that have not been widely appreciated. The apparent localization of volume-regulating recpetors to the left atrium and the accumulating evidence that atrial receptors do respond to changes in atrial pressure or atrial volume triggered a myriad of further studies on the function of left receptors. Nearly all these studies employed indirect techniques that produced changes in systemic and pulmonary hemodynamics in addition to changes in left atrial pressure. Nevertheless, it often was assumed that if changes in left pressure were produced, any concomitant changes in circulating ADH or in urine flow were attributable to a reflex elicited from atrial receptors. Mush of the data obtained were interpreted as being compatible with the elft atrial volume-receptor hypothesis, but very liggle of the data pertained to left atrial receptors specifically.