John S. Schroeder, MD

View details for Web of Science ID A1997XU85600003

View details for PubMedID 9315517

View details for Web of Science ID A1995RR84000013

View details for PubMedID 7637732

Abstract

Evidence that calcium antagonists can suppress diet-induced atherosclerosis in the thoracic aorta of animals has existed for a decade. Recently, the results of quantitative angiographic trials of calcium antagonists in humans have become available, confirming their beneficial effect on coronary artery disease. Nifedipine treatment reduces the rate of new lesion development in patients with mild-to-moderate coronary artery disease, reduces disease progression, and, in some cases, induces lesion regression. There is evidence that the use of verapamil may be associated with lesion regression and stenosis prevention, and that nicardipine may influence the progression of minimal coronary lesions. Theoretically, a wide range of explanations for an effect of calcium antagonists on atherogenesis is possible. Potential mechanisms include preventing calcium overload, upregulating LDL receptors with enhanced LDL clearance, inhibiting cell migration into the arterial wall, and antiplatelet effects. The exact mechanism remains unclear, but alteration of serum lipid levels and blood pressure does not appear to be the common pathway. Work with humans is still preliminary, and longer follow-up and further trials are required to determine the appropriate clinical application of calcium timing for their introduction.

View details for PubMedID 1654938

View details for Web of Science ID A1991FR68100009

View details for PubMedID 2038369

View details for Web of Science ID A1990EJ51000039

View details for Web of Science ID A1989CB17700017

View details for Web of Science ID A1988N612000009

View details for Web of Science ID A1987L004500011

View details for Web of Science ID A1986E294200011

View details for PubMedID 3531855

View details for Web of Science ID A1986D114700001

Abstract

To determine the effects of diltiazem hydrochloride on patients with paroxysmal supraventricular tachycardia, we administered intravenous diltiazem, 0.25 mg/kg to patients who presented to the Stanford Medical Center Emergency Department with this rhythm. Blood pressure was recorded prior to administration, and monitored for 20 min thereafter. Six of the ten patients converted to sinus rhythm a mean of 7.75 min (+/- 4.4) after drug administration. The remaining four experienced slowing of heart rates from a mean of 177 to 166 beats/min. Systolic blood pressure fell a mean of 12.4 mmHg during treatment, but returned to pretreatment level or higher within 20 min following diltiazem administration. This mean degree of blood pressure reduction compares favorably with effects produced by intravenous verapamil under comparable circumstances. Intravenous diltiazem appears to be a safe and effective drug for the conversion of paroxysmal supraventricular tachycardia.

View details for Web of Science ID A1986A709500004

View details for PubMedID 3720041

View details for Web of Science ID A1985AUR1900090

Abstract

The excellent safety and predictable efficacy of isosorbide dinitrate (ISDN) have been demonstrated repeatedly during the past 25 years in a number of studies in which the agent has been used alone or in combination with other antianginal agents. Clinical studies to investigate the additive or synergistic effect of ISDN have been difficult to conduct because of the complexity of protocol design and length of studies required. However, combination therapy is well accepted in the clinical practice of medicine and cardiology and is used to obtain additive therapeutic effects while minimizing the side effects. The addition of ISDN not only to other standard and proven antianginal agents but also to calcium antagonists should prove to be a fruitful area for further clinical research benefiting patients with angina pectoris (caused by either coronary artery spasm or occlusive coronary artery disease), hypertension, and congestive heart failure. Noncardiovascular uses of ISDN may include the treatment of hyperspasticity of other smooth muscle beds, such as esophageal spasm and achalasia.

View details for Web of Science ID A1985ALZ1200018

View details for PubMedID 3893082

Abstract

A cardiac transplant patient with rapidly progressive graft atherosclerosis is described. This case demonstrates the accelerated nature of this disease and problems in diagnosis, as well as an unexpected and previously unreported lack of sensitivity of exercise thallium scintigraphy in its investigation. This case also gives further support to the practice of routinely and frequently obtaining coronary arteriograms in the management of these patients.

View details for Web of Science ID A1985ALK9200040

View details for PubMedID 3891822

Abstract

Electrocardiograms of 65 patients treated with dothiepin, a sulphur substituted tricyclic antidepressant, were compared to those of 57 patients receiving amitriptyline and 62 patients given placebo. Amitriptyline produced an average heart rate increase of 10 beats/minute as compared to 5 beats/minute for dothiepin (p less than .02). Amitriptyline also produced a significant prolongation of the corrected QT interval as compared to both dothiepin and placebo (p less than .01 and p less than .001, respectively). Dothiepin had no significant effect on any index of myocardial conduction (PR interval, corrected QT interval, and QRS duration) as compared to placebo.

View details for Web of Science ID A1984TB30000002

View details for PubMedID 6376479

Abstract

We evaluated the effects of isoproterenol in right ventricular papillary muscles derived from normal and failing isolated human hearts. Basal values for the peak force developed, rate of force development (dF/dt), and time to peak tension (TPT) were similar in both groups. Isoproterenol produced a significantly smaller (p less than 0.05) increase in peak force developed and dF/dt in failing papillary muscles. The half equivalent dose (ED50) of isoproterenol was fivefold higher in failing muscle as compared to normal muscle. We conclude that failing cardiac muscle demonstrates decreased responsiveness to beta-receptor mediated stimulation.

View details for Web of Science ID A1983RE66300016

View details for PubMedID 6308994

Abstract

In 43 patients with variant angina, the cardiovascular event rate during diltiazem therapy was compared with that in an equal time period before initiation of therapy. Cardiovascular events, that is, myocardial infarction, sudden death and hospitalization for prolonged angina, were decreased significantly (p less than 0.01) during the initial 6 months and mean 19.6 months of therapy. Based on the binomial principle, there were 22 events during the mean 19.6 months before therapy and 2 events during the equal time period on therapy. No patient died during follow-up. The frequency of angina was decreased by 94%. Diltiazem was well tolerated by all patients and no patient had to discontinue therapy because of adverse effects. It is concluded that long-term diltiazem therapy reduces cardiovascular events in patients with variant angina.

View details for Web of Science ID A1983QR88000020

View details for PubMedID 6853903

View details for Web of Science ID A1983PY90800003

View details for Web of Science ID A1983RD90200012

View details for PubMedID 6872168

View details for Web of Science ID A1983QN22500021

View details for Web of Science ID A1982NQ15100004

View details for PubMedID 6125054

Abstract

The slow channel blocking agents--diltiazem, verapamil and nifedipine--have generated clinical interest for the treatment of a variety of cardiovascular disorders. These agents, despite a similar basic mechanism of action, produce disparate clinical cardiac electrophysiologic effects in human beings. In usual doses, the acute administration of diltiazem slows heart rate. Verapamil and nifedipine, however, increase heart rate. Although diltiazem and verapamil produce equivalent slowing of atrioventricular (A-V) nodal conduction, verapamil prolongs A-V nodal refractoriness to a greater degree. In contrast, nifedipine facilitates A-V nodal conduction and shortens A-V nodal refractoriness. Knowledge of these differences may aid in the appropriate selection of specific slow channel blocking agents in specific clinical situations.

View details for Web of Science ID A1982ND14800022

View details for PubMedID 6277182

View details for Web of Science ID A1982NC62700007

View details for Web of Science ID A1982NG44900005

View details for PubMedID 6120768

View details for Web of Science ID A1982NE31000007

Abstract

To facilitate the outpatient diagnosis of variant angina by documenting transient ST segment evaluation during chest pain, we studied the feasibility of transtelephonic ECG monitoring during angina episodes. Eight patients with known coronary artery spasm underwent simultaneous continuous ambulatory and transtelephonic ECG monitoring during a 24-hour period. Five patients (62%) had transient diagnostic ST segment shifts on both continuous ambulatory and transtelephonic monitoring. Another eight patients with coronary spasm underwent 24-hour continuous ambulatory monitoring and separate 14-day period of transtelephonic monitoring. The addition of this longer monitoring period provided diagnostic ST segment shifts in three patients. We conclude that transtelephonic monitoring in patients with suspected coronary artery spasm can provide important additional diagnostic information to continuous ambulatory monitoring, particularly in the patient with infrequent or predictable chest pain.

View details for Web of Science ID A1981MB29100009

View details for PubMedID 7258093

Abstract

The mechanism of coronary artery spasm has been poorly understood but there has been some suggestion that cardiac autonomic innervation may play an important role. We report coronary artery spasm in a 43 year old man two years after he had received a transplant. Provocative pharmacologic testing suggested functional denervation of the patient's heart. Thus, coronary artery spasm can occur in the transplanted, denervated human heart. Autonomic innervation of the heart is not essential in all cases of coronary spasm, and circulating catecholamines and/or metabolic of hormonal products may play an important role.

View details for Web of Science ID A1981LP92100027

View details for PubMedID 7015853

Abstract

Obstructive sleep apnea syndrome (OSAS), a disabling disorder that leads to life-threatening cardiorespiratory events during sleep, has been treated by tracheostomy. This article reports long-term follow-up data of 50 patients who have undergone this procedure, and the indications for surgery are summarized. Surgery may result in secondary local and general acute and subacute complications, but, on a long-term basis, patients were completely relieved of clinical symptoms, returned to full activity, and adapted normally to social and familial life. Temporary closure of the tracheostomy during sleep led to recurrence of obstructive sleep apnea.

View details for Web of Science ID A1981LY00900005

View details for PubMedID 7247605

View details for Web of Science ID A1981LR85000021

View details for Web of Science ID A1981MG28900018

View details for Web of Science ID A1980JE11500005

View details for Web of Science ID A1980JN03200014

View details for Web of Science ID A1980KC27400004

View details for PubMedID 6773405

View details for Web of Science ID A1980KF18900002

View details for Web of Science ID A1980KK58600004

Abstract

Medical therapy for Prinzmetal's variant angina has been treatment of the acute attack with sublingual nitroglycerin. Prophylactic therapy has been more difficult, utilizing long-acting vasodilators that are limited because of their short half-life and side effects when therapeutic doses are used. Alpha-adrenergic blockade has been effective in some patients but is frequently associated with intolerable side effects or apparent development of tolerance to the drug. Preliminary experience from a randomized double-blind trial of diltiazem, a new calcium antagonist, has demonstrated a 90% reduction in pain episodes, with many patients becoming pain-free on the 240-mg daily dose. These data and the lack of adverse side effects demonstrate a dramatically effective therapy for patients with coronary artery spasm.

View details for Web of Science ID A1980KF18900017

View details for PubMedID 6772386

Abstract

The functional behaviour and pharmacological responses of ring segments of large coronary arteries removed from five patients undergoing cardiac transplantation were studied in vitro. All segments showed spontaneous rhythmic contractions which were markedly dependent on external calcium and were rapidly abolished in calcium-free solutions and by verapamil. The contractions were inhibited by cooling and by anoxia. Phasic activity was enhanced by increasing the external potassium concentration over the range 5 to 20 mmol.litre-1 but was abolished by 120 mmol.litre-1 potassium. Noradrenaline and ergonovine enhanced or induced phasic activity. The behaviour of human coronary arteries resembles that of the portal-mesenteric veins of many species and our results suggest that the activation mechanisms of these two tissues may be similar.

View details for Web of Science ID A1980KR90700009

View details for PubMedID 6783306

View details for Web of Science ID A1979GQ02500067

View details for PubMedID 377649

View details for Web of Science ID A1979GU91000029

View details for PubMedID 372605

Abstract

Because pulmonary hypertension and systemic hypertension occur during sleep-induced obstructive apnea, six patients underwent overnight hemodynamic monitoring before and after tracheostomy. Variables studied included heart rate, pulmonary artery pressure, femoral artery pressure, and arterial oxygen tension (Po2). After tracheostomy, significant reductions were noted during sleep in mean pulmonary artery pressure from 45 +/- 6 mm Hg (mean +/- SEM) to 22 +/- 2 mm Hg (P less than 0.05) and in mean femoral artery pressure from 137 +/- 6 mm Hg to 97 +/- 3 mm Hg (P less than 0.005). There was also a significant increase for the group in arterial Po2 recorded during the apneic episodes from 38 +/- 3 mm Hg before tracheostomy to 71 +/- 2 mm Hg (P less than 0.001) after tracheostomy. We conclude that tracheostomy improves the hemodynamic abnormalities and hypoxemia that occur during sleep in patients with sleep-induced obstructive apnea.

View details for Web of Science ID A1978FR76800003

View details for PubMedID 697223

View details for Web of Science ID A1978EZ47900003

View details for PubMedID 645739

View details for Web of Science ID A1978EM88500004

View details for PubMedID 343649

Abstract

A patient with autonomic insufficiency and extrapyramidal signs (Shy-Drager syndrome) and sleep apnea syndrome (SAS) underwent hemodynamic studies. In comparison to patients with SAS and intact autonomic reflexes, systemic hypertension was absent and marked sinus arrhythmia during sleep was blunted. Cyclical pulmonary hypertension associated with frequent apneic episodes during sleep persisted, reflecting a minor role of autonomic reflexes in the generation of this abnormality. Autopsy confirmed the Shy-Drager syndrome and multiple areas of degeneration were observed in areas of the CNS outside the medullary respiratory centers, suggesting their importance in the origin of the respiratory abnormalities in SAS.

View details for Web of Science ID A1978EV05400008

View details for PubMedID 626549

Abstract

Cardiac retransplantation has been performed in five patients at Stanford University Medical Center. Long-term survival and rehabilitation have been achieved in two cases. In the first case retransplantation was performed 57 days after the initial procedure because of persistent acute graft rejection. The second patient underwent retransplantation 27 months postoperatively because of documented accelerated graft atherosclerosis. The major indications for cardiac retransplantation consist of intractable acute rejection and late postoperative graft atherosclerosis. These complications should prompt consideration of cardiac retransplantation in carefully selected cases.

View details for Web of Science ID A1977CV61800014

View details for PubMedID 319302

Abstract

Cardiac arrhythmias during wakefulness and sleep in 15 patients with sleep-induced obstructive apnea, and the effect of atropine and tracheostomy on these arrhythmias were studied by continuous overnight Holter electrocardiographic, respiratory and electroencephalographic recordings. Sleep was characterized by marked sinus arrhythmia in 14, extreme sinus bradycardia ( less than 30 beats/minute) in six, asystole of 2.5 to 6.3 seconds in five, second degree atrioventricular (A-V) block in two, and ventricular arrhythmias--complex premature ventricular beats in 10 and ventricular tachycardia in two. Arrhythmias during wakefulness were limited to premature ventricular beats in six. Atropine administration was partially and tracheostomy highly effective in preventing the majority of these arrhythmias during sleep. Marked sinus arrhythmia during sleep is characteristic of the syndrome of obstructive sleep apnea and is frequently accompanied by potentially life-threatening tachy- and bradyarrhythmias. Possible mechanism of production of these arrhythmias, the mode of action of tracheostomy and atropine, and the probable role of similar arrhythmias in the sudden infant death syndrome are discussed.

View details for Web of Science ID A1977DV42100005

View details for PubMedID 331948

Abstract

The medical literature since 1900 has been reviewed to determine the nature of lithium's cardiovascular effects. In therapeutic doses, lithium produces reversible T wave flattening and inversion in the electrocardiogram: rarely, it may cause sinus node dysfunction or ventricular arrhythmias. Patients with lithium toxicity almost always present with neurologic signs and symptoms. "Hypotension and cardiovascular collapse," alleged cardiotoxic manifestations of lithium, invariably follow days of coma. Given the possible cardiotoxic effect other psychopharmacologic agents and the hazards of withholding effective therapy in mania, it is concluded that lithium may be used safely in patients with cardiac disease if the dose is adjusted to the rate of lithium excretion and if serum levels of lithium are followed carefully. When used in patients with cardiac arrhythmias, frequent electrocardiographic monitoring is advised.

View details for Web of Science ID A1976CL02900011

View details for PubMedID 790953

Abstract

Eleven of 21 consecutive patients with Prinzmetal angina (PMA) exhibited no significant fixed stenoses of the coronary arteries. Spontaneous coronary arterial spasm was demonstrated in 3 patients. Ergonovine maleate produced near-total occlusion of a major vessel in 3 of 4 other patients with PMA, but did not provoke spasm in 10 without PMA. The current study documents spasm as the mechanism of myocardial ischemia in some patients with normal coronary arteries and provides initial and favorable diagnostic results with provocative pharmacoangiography in this entity.

View details for Web of Science ID A1976BR92300002

View details for PubMedID 935383

Abstract

Coronary arteriography performed in 17 patients with Prinzmetal's variant angina demonstrated high grade fixed obstructions in 9 patients (Group I) and insignificant or no fixed lesions in 8 patients (Group II). Group I consisted mostly of middle-aged or elderly men with S-T segment elevations in various sites; Group II included five younger women with S-T segment elevations in inferior electrocardiographic leads. In Group I patients, arteriography revealed a discrete high grade lesion located proximally in a major coronary artery in four patients and multivessel involvement in five patients. In Group II patients, spontaneous spasm was documented in three patients and spasm was pharmacologically provoked in two others during arteriography. The current study indicates that spasm is the responsible pathogenetic mechanism of myocardial ischemia in some patients with Prinzmetal angina and that this mechanism may be suspected from the clinical characteristics of these patients.

View details for Web of Science ID A1976BQ73700002

View details for PubMedID 1266748

View details for Web of Science ID A1976BZ10600031

View details for PubMedID 947075

Abstract

Twelve patients with predominantly obstructive type sleep apnea underwent cardiac catheterization, hemodynamic monitoring, and arterial blood gas analysis during wakefulness and sleep. Abnormalities during wakefulness included systemic hypertension in four of 12, exercise-induced mild pulmonary hypertension in five of 12, and alveolar hypoventilation in one. During sleep nine patients had cyclic elevations of arterial pressure with each apneic episode, exceeding 200 mm Hg systolic in three of 12. Pulmonary artery pressures increased in 10 of 12, exceeding 60 mm Hg systolic in five. Marked degrees of hypoxemia (arterial P02, less than 50 mm Hg in eight of 12) and moderate hypercapnia with respiratory acidosis were associated with these hemodynamic changes. Cyclic upper airway obstruction during sleep may result in hypercapnia, acidosis, and pronounced hypoxemia, which can lead to hemodynamic abnormalities during sleep. Sustained pulmonary hypertension and possibly systemic hypertension may follow. Tracheostomy is an effective therapy and is recommended to symptomatic patients who have predominantly obstructive apnea but no relievable anatomic cause of upper airway obstruction.

View details for Web of Science ID A1976CP46600002

View details for PubMedID 999107

View details for Web of Science ID A1976BQ73700012

Abstract

Twelve adult patients with ostium primum atrial septal defects (incomplete endocardial cushion defect) who underwent surgical repair of their lesions were evaluated in the late postoperative period. All had closure of the low-lying atrial septal defect, with suturing of the mitral valve cleft in 11 patients. Although the patients benefited symptomatically from the surgery, all had residual cardiac murmurs. Postoperative cardiac catheterization and left ventriculography in eight revealed successful closure of the atrial septla defect, but three demonstrated residual mitral insufficiency. In spite of the successful surgical repair in these patients, bacterial indocarditis prophylaxis should be continued in view of the residual murmurs and valvular abnormalities.

View details for Web of Science ID A1975V416900013

View details for PubMedID 123190

Abstract

An improved technique for identification, diagnosis and quantification of arrhythmias during rest or ambulatory electrocardiographic recording is described. With simultaneous plotting of the R-R interval and the QRS duration and QRS vector measurement of each beat versus time, all periods of arrhythmias or abnormal complexes can be identified and characterized. Analog electrocardiographic samplings are used to confirm the diagnosis of the arrhythmia and to exclude artifact. The availability of a permanent record for the characterization of each QRS complex enables the physician to check the technician's analysis of the recording and to relate all events to the patient's heart rate and clinical symptoms. This technique also provides data for quantification of ventricular arrhythmias.

View details for Web of Science ID A1975AE53700008

View details for PubMedID 48334

Abstract

Endomyocardial tissue, obtained from two patients presenting with restrictive cardiomyopathies, demonstrated amyloid infiltration. The percutaneous transvenous cardiac biopsy technic, using a modified Konno-Sakakibara cardiac bioptome, was safe and quick. Physical examination and catheterization data may not provide a definite differential diagnosis between restrictive and constrictive myocardial disease. Confirmation by biopsy of the cardiac amyloidosis assisted in providing optimum diagnostic and therapeutic care for these patients.

View details for Web of Science ID A1975AM28400015

View details for PubMedID 1098458

Abstract

In order to study the occurrence and frequency of ischemia-induced ventricular arrhythmias, we analyzed 105 episodes of spontaneous angina pectoris occurring at rest in 28 hospitalized patients with unstable angina pectoris and proved coronary artery disease. Of 24 patients with serious ventricular arrhythmias during pain, 17 (57%) were arrhythmia-free during monitoring. In the other four patients, 17 of 29 (59%) pain episodes were associated with serious ventricular arrhythmias, and three of these four had serious ventricular arrhythmias during pain-free periods. Each patient tended to manifest the same type of arrhythmia during repeat episodes of pain. It appears that continuous electrocardiogram (ECG) monitoring is important during the initial hospitalization of the patient with unstable angina. The presence of ventricular arrhythmias during pain-free periods indicates a high risk for serious ventricular arrhythmias during episodes of spontaneous pain. These patients should be considered for continued ECG monitoring and antiarrhythmic therapy.

View details for Web of Science ID A1975AZ11300002

View details for PubMedID 54051