The central haemodynamics at rest and during exercise have been studied in 25 patients with complete AV block who were treated with fixed rate (FRP) and atrial triggered pacemakers (ATP). The aim of the investigation has been to study the effect of a synchronized atrial contraction for the filling of the ventricles and for the cardiac output (Q). Pressures and Q have been determined during heart catheterization. The P wave for triggering the atrial synchronized pacemaker has been obtained with an electrode in close contact with the atria, introduced by means of mediastinoscopy. The study consists of two series. In the first series (12 patients) the central haemodynamics were recorded with each patient connected first the FRP (about 70 impulses/min) and later to the ATP. Most patients were studied both at rest and during exercise, the work loads being identical with both types of pacemakers. Q at rest is 10% higher with ATP (p < 0.02) than with FRP and during exercise 20 % higher with ATP (p < 0.01). Stroke volume (SV) at rest is equal with both types of pacemakers, but significantly larger with FRP during work (p < 0.001). The left ventricular (LV) filling pressure is significantly lower (p < 0.01) with ATP at rest, but not during exercise (p < 0.8). In the second series 13 patients were studied at rest and during exercise. The recordings of pressures and Q were first performed with the patient on ATP. After 30 min rest an identical study was performed with the patient connected to FRP, the rate of which was matched (FRPm) to that previously recorded with ATP. Q at rest is 18% higher (p < 0.01) with ATP than with FRPm and during work 8 % higher (p < 0.05) with ATP. SV at rest is significantly larger (p < 0.01) with ATP than with FRPm, whereas during exercise no significant difference is observed between the two types of pacemakers. LV filling pressure at rest is significantly lower on the 5 % level with ATP; during exercise no significant difference is observed. The investigation shows that in many patients, especially younger ones, treatment with ATP makes it possible to obtain a larger Q during exercise, and thus to increase the oxygen transporting capacity of the circulation. This benefical effect may be more pronounced in patients with low compliance of the ventricular myocardium.

Haemodynamic effect of atrial triggered versus fixed rate pacing at rest and during exercise in complete heart block

The pacemaker syndrome is a complex of clinical signs and symptoms related to the adverse hemodynamic and electrophysiologic consequences of ventricular pacing in the absence of other causes. Neurologic symptoms or those suggesting low cardiac output or congestive heart failure, temporally related to the onset of ventricular pacing, are indicative of the pacemaker syndrome. The evolution of a clinically recognized syndrome, an analysis of possible mechanisms and clinical manifestations, and diagnostic approaches and their implications for management are discussed.

The Pacemaker Syndrome

We present the results of a 12-year retrospective analysis of 11 patients, eight women and three men, aged 16-76 years, with pathologically documented atrial myxomas. Nine of the 11 patients were found to have a left atrial myxoma; right atrial myxomas were identified in two. Five of the 11 patients (45%) had abnormalities on neurologic examination, and five of five had computed tomographic evidence of nonhemorrhagic cerebral infarction. Neurologic symptoms were the initial presentation in four patients. Six patients reported a history of cardiac disease; eight of the 11 had abnormalities on cardiac auscultation. Echocardiography in 10 patients was diagnostic in all but one. Gated magnetic resonance imaging of the heart in two patients demonstrated myxoma position and movement. Follow-up examinations (varying from 1 month to 7 years after tumor resection) in nine of 11 patients demonstrated no recurrent neurologic symptoms. Cerebral infarction is a common complication of atrial myxomas and may be the presenting feature. Recurrent cerebral emboli before surgery is not uncommon. Cardiac auscultation may be normal, and electrocardiographic changes are often nonspecific. Delayed neurologic events following surgery are rare.

Neurologic manifestations of atrial myxoma. A 12-year experience and review.

Extracranial vertebrobasilar artery thrombo-occlusive disease may cause repetitive transient ischemic episodes and, less frequently, brain-stem or cerebellar infarction. This report describes 40 patients who experienced repetitive vertebrobasilar ischemic symptoms despite maximal medical therapy. The natural history, pathogenesis, and treatment options for each causative lesion are reviewed. The operative approaches to symptomatic disease of the proximal vertebral arteries, arterial compression by cervical osteophytes, traumatic lesions of the vertebral arteries, and thrombo-occlusive pathology of the distal extracranial vertebral arteries are outlined. Specific anesthetic and surgical techniques that have proved successful while achieving zero operative mortality and low perioperative morbidity rates are reported.

Vertebrobasilar insufficiency. Part 1: Microsurgical treatment of extracranial vertebrobasilar disease

An aneurysm is a focal dilatation of an arterial blood vessel. Luminal forces, such as high blood flow, shear stress and turbulence, are implicated in the pathogenesis of intracranial aneurysms, and luminal characteristics, such as sac size and morphology, are usually essential to the clinical decision-making process. Despite frequent clinical emphasis on the vessel lumen, however, the pathology underlying the formation, growth and rupture of an aneurysm mainly resides in the vessel wall. Research on the morphology and histopathology of the vessel wall reveals that intracranial aneurysms do not constitute a single disease, but are a shared manifestation of a wide range of diseases, each of which has a unique natural history and optimum therapy. This Review classifies intracranial aneurysms by vessel wall pathology, and demonstrates that understanding the morphology and pathology of this structure is important in determining the therapeutic approach. The article concludes that aneurysms represent a symptom of an underlying vascular disease rather than constituting a disease on their own.

Intracranial aneurysms: from vessel wall pathology to therapeutic approach

Cerebral embolization of tumor tissue is a well known complication in patients with left heart myxomas (11). Surprisingly, cerebral angiography has rarely been employed in evaluation, and, even in the few cases in which it has been performed (2, 3, 6, 15), little discussion of the findings and only one set of reproductions (6) are presented in the literature. The purpose of this paper is to present a short review of this subject and report 2 cases in which angiocardiographic and pathologic demonstration of left heart myxomas were coupled with cerebral angiograms showing cerebral vascular abnormalities. Review Metastatic lesions constitute 90 to 95 per cent of all cardiac tumors, but of the primary tumors approximately 50 per cent are myxomas (13, 14). About 75 per cent arise in the left atrium. The majority of the others originate in the right atrium (14), with only 4 reported in the left ventricle (7, 12, 17, 18). Few typical clinical features exist (4, 5, 8, 9). The lesion may be entirely silent clinica...

Radiologic observations in cerebral embolization from left heart myxomas.

The subclavian steal syndrome.

CC ARDIAC TUMORS are relatively infrequent lesions which have assumed clinical importance as successful methods for inu'acardiac surgery have been developed . Recent reports indicate the increasing frequency of accurate preoperative diagnosis and the successful removal of such minors . ] 36 The first recorded primary cardiac tumor, described by Columbus'' in 1559, arose within the left ventricular cavity. Since that time approximately 550 priniarv tumors of the heart have been reported. Over 300 have been mvxomas. This tumor typically arises from the atrial septum in the region of the fossa oxalis . It is three time , more frequent in the left atrium than in the right .' s" In twenty-one instances the diagnosis has been made antemortem and in thirty cases Irtyxomas have been discovered during surgical exploration for mitral or tricuspid stcnosis . Intracardiac tumors may occur at any age . The majority have developed in patients between the ages of thirty and sixty veers. The incidence has been greater in women . The usual clinical manifestations arise front obstruction of the mitral or tricuspid valve . In recent years angiocardiography has resolved many of the difficulties inherent in establishing an accurate preoperative diagnosis ." 11 Until the advent of technics for stasis cardiotouiy and temporary cardiopulmonary bypass whielt permit the excision of such tumors under direct vision, attempts at removal of intracardiac tumors were crude and inexact ."2 Because an accurate preoperative diagnosis of a primary cardiac tumor or thrombus can he made if certain clinical and rocnlgenographic characteristics arc kept in mind . our experience with the following three cases is presented to elucidate the diagnostic features and characteristics of such lesions . In the first patient (Case 1), a right ventricular myxoma was suspected on clinical examination and confirmed by angiocardiography . This tumor arose within the right atrium and had prolapsed through the tricuspid valve into the right ventricular cavih . In the Second case a large left atrial thrombus, not suspected prior to death, was revealed on postmortem examination in an elderly woman with emboli in the pulmonary and mesenteric arteries and subsequent extensive infarction . In the third case, postmortem examination revealed a large mural thrombus cornpletely filling the distal two-thirds of the left ventricular cavity with multiple moral thrombi within the cardiac chambers . Chronic myocarditis was responsible for the thrombi and death resulted from low cardiac output and multiple pulmonary and systemic emboli. Peripheral emboli and a low cardiac output were responsible for gangrene of the right foot, right fourth finger and third left toe .

Harold A. Collins

Papers

Radiologic observations in cerebral embolization from left heart myxomas.

The subclavian steal syndrome.

Intracardiac myxomas and thrombi: Clinical manifestations, pathology and treatment

Tracheoesophageal fistula resulting from nonpenetrating trauma to the chest.

Physiological studies and clinical experience in patients with synchronous and asynchronous pacemakers.