Validation of advanced ECG diagnostic software for the detection of prior myocardial infarction by using nuclear cardiac imaging

The investigators report the diagnostic performance of the latest version (Version 2.5) of the recently developed Cardiovise algorithm for detecting prior myocardial infarction (MI). The Cardiovise 2.5 prior MI algorithm, a component of Cardiovise Cardiac Diagnostic System (Inovise Medical, Inc, Newberg, OR), uses scalar QRS, scalar T wave, and vectorcardiographic QRS criteria for detecting, sizing, and localizing prior MI. In this study only the detection part of the algorithm's performance was evaluated, using 105 patients with and 98 patients without prior MI as indicated by the results of cardiac imaging with Sestamibi. The specificity, and sensitivity of Cardiovise 2.5 for detecting prior MI in this population of patients are 97% and 79%, respectively. The sensitivity and overall diagnostic performance of Cardiovise 2.5 was significantly better than those of a total of 6 human readers (3 cardiologists and 3 primary care physicians) and to 2 commercially available ECG diagnostic algorithms.

A dynamic three-dimensional display of ventricular excitation and the generation of the vector and electrocardiogram

Computer models, such as those produced by Solomon and Selvester, have helped increase our understanding of the heart's electrical activity. In the present report, we describe a dynamic three-dimensional computerized display of the myocardial excitation sequence that is based on this fundamental research. The display is based on the vectors of the potential differences generated in the various parts of the myocardium during its excitation. The sums of these individual vectors form composite vectors that are related to the ECG signals recorded from the body's surface. The display simultaneously portrays the temporal changes of the composite vectors in 3 dimensions and in each plane (the transverse, frontal and left sagittal). It also shows the corresponding changes in the QRS complexes in each of the 12 scalar ECG leads. The display shows the patterns of activation of the normal heart and an example of posterolateral myocardial infarction. The technique facilitates the understanding of myocardial activation and how it is modified by specific pathological conditions. It is believed that this method of presentation and visualization of the generation of the ECG will be of value in the teaching of this process.

The correlation between presenting ST-segment depression and the final size of acute myocardial infarcts in patients with acute coronary syndromes

The use of reperfusion therapy in patients with ST elevation acute coronary syndromes had been established. However, reperfusion therapy is usually considered contra-indicated in those with ST depression, despite the knowledge that regional posterior infarction is typically indicated by ST depression maximal in leads V1 to V3 and nonregional subendocardial infarction is typically indicated by marked ST depression maximal in other leads. This study of patients with non-ST-elevation acute coronary syndromes investigates the quantitative relationship between presenting ST depression and final QRS changes in both of these subgroups. The final QRS score was significantly higher (2.44 points) than that of a control group with not ST depression, (1.55 points) in the group with maximal ST depression in V1 to V3 (P = 0.04). However, in the entire population, there was a highly significant correlation (P = .003) between the sum of the presenting ST depression and the final QRS score. Trials of reperfusion therapy will be required to determine if such evolution to electrocardiogram documented acute myocardial infarction can be prevented in patient with marked ST depression acute coronary syndromes.

Comparison of an automated thrombolytic predictive instrument to both diagnostic software and an expert cardiologist for diagnosis of an ST elevation acute myocardial infarction

Because the electrocardiograms (ECGs) of patients with symptoms suggesting an acute thrombotic coronary occlusion are typically read by physicians relatively inexperienced in this skill, it is important to develop automated decision support. A Thrombolytic Predictive Instrument (TPI) is now available along with the standard diagnostic software in a commercially available electrocardiograph. This study evaluates the performance of the predictive software in comparison to both an expert cardiologist and standard diagnostic software. True sensitivity and specificity cannot be determined because acute coronary angiography was not performed. The specificities determined by this study were excellent (98% and 99%), and the sensitivities were very good (72% and 78%). These results that the TPI will be only rarely applied to patients who do not indeed have an acute coronary thrombosis. However, the reasons for even this small number of presumably falsely TPI positive patients should be determined and analyzed. It is unlikely that alterations of the thresholds for TPI activation will significantly improve on this very good level of sensitivity, without prohibitively decreasing specificity.

Standards for the function of an academic 12-lead electrocardiographic core laboratory

An academic 12-lead electrocardiogram (ECG) core laboratory aims to provide the highest possible quality ECG recording, measurement, and storage to aid clinicians in research into important cardiovascular outcomes and to maximize the credibility of scientific results based solely, or in part, on ECG data. This position paper presents a guide for the structure and function of an academic ECG core laboratory. The key functional aspects are: 1) Data collection, 2) Staff composition, 3) Diagnostic measurement and definition standards, 4) Data management, 5) Academic considerations, 6) Economic consideration, and 7) Accreditation. An ECG Core Laboratory has the responsibility for rapid and accurate analysis and responsible management of the electrocardiographic data in multicenter clinical trials. Academic Laboratories, in addition, provide leadership in research protocol generation and production of research manuscripts for submission to the appropriate peer-review journals.

Importance of accounting for the variability of electrocardiographic data among diagnostically similar patients with inferior wall healed myocardial infarction

The authors describe a method to account for patient-to-patient variability in electrocardiographic data. The method yielded criteria for healed inferior myocardial infarction with diagnostic performances better than those of traditional electrocardiographic parameters.

Using digital versus analog ECG data in clinical trials

In 54 patients, we measured 3 different electrocardiogram (ECG) parameters required in the Symphony 1 trial and compared various combinations of pairs of measurements from 4 different sets of analog data and 1 set of digital data. Particularly for measurements of the durations of R waves in lead aVF, we found poor intraobserver and interobserver reliability and poor agreement between analog and digital data. There was much better agreement in measurements of the amplitudes of S waves in lead V3. The poorer agreement involving durations appears to be due to difficulties in accurately identifying the offsets of portions of the QRS complex, especially in lead AVF. We conclude that, particularly in measurements of duration, digital and analog data are not equivalent.

Using directly acquired digital ECG data to optimize the diagnostic criteria for anterior myocardial infarction

The use of a newly developed method of directly transferring digital data from Marquette electrocardiogram (ECG) systems (Milwaukee, Wisconsin) to personal computers for subsequent storage and analysis is illustrated. This method can eliminate the slowness and inaccuracy associated with measuring relevant ECG parameters from analog tracings and manually entering the data into a computer. In this study, the new method was used to derive ECG criteria for anterior myocardial infarction and to compare their performances to those of the current Marquette 12SL diagnostic program and of a group of cardiologists who had also interpreted the ECGs. Using angiographic data, 82 normal subjects and 55 patients with anterior myocardial infarction were identified. The digital ECG data from the patients in each group were transferred to a personal computer and frequency distributions of these data were generated. From these frequency distributions, the ECG criteria that most reliably separated the two groups were identified. The diagnostic performance of the best of these empirically derived criteria appears clinically superior to the performances of both the 12SL program and the cardiologists who had also interpreted the ECGs.

An analysis of symptoms in patients with permanent ventricular pacemakers

The prevalence and severity of symptoms of the "pacemaker syndrome" were investigated in 64 patients with VVI pacemakers and compared, in the same patients, to a series of control symptoms, unrelated to pacemaker function. Symptoms were also compared in patient groups unlikely to have the "pacemaker syndrome" (atrial fibrillation), most likely to have such symptoms (retrograde atrial activation) and in an intermediate group (competitive paced and sinus rhythms). There was a linear relationship between the frequency and severity of "pacemaker" symptoms and control questions in all groups and no preponderance of "pacemaker" symptoms in any group. The study provides an estimate of the number and severity of symptoms in patients with VVI pacemakers, demonstrates the non-specificity of the "pacemaker syndrome" and shows no evidence of a sub-clinical "pacemaker syndrome" in the patients observed.

Mitral valve prolapse and neuroticism in chest pain patients with normal and diseased coronary arteries

Patients with chest pain and normal coronary arteries (NCA) score higher on measures of neuroticism than patients with coronary artery disease (CAD). This relationship, coupled with findings linking mitral valve prolapse (MVP) and anxiety disorders, led us to examine prospectively the possibility that a greater incidence of MVP among NCA patients accounts for their elevated neuroticism scores. One-hundred-forty-four patients completed psychological tests and a structured interview prior to cardiac catheterization. Forty-one of the 144 patients (28%) had normal coronary arteries. Within the NCA group 29 percent had MVP; within the CAD group only 13 percent had MVP. Despite the significant difference between NCA and CAD groups on measures of neuroticism, there were no differences as a function of MVP status, nor was there an interaction of MVP and coronary arterial status. These findings support the case for an association between NCA and neuroticism independent of the presence or absence of MVP.

Use of hepatic vein catheterization in the evaluation of patients with anasarca

In patients with anasarca, the relative importance of cardiac, pulmonary and/or hepatic dysfunction is often difficult to determine. Conventional use of the Swan-Ganz catheter helps to separate the contributions of right and left heart disease, but it is seldom used to evaluate liver dysfunction. This report describes passage of a Swan-Ganz catheter into the hepatic vein prior to pulmonary artery placement in 11 patients. Hepatic vein catheterization permitted wedged hepatic venography using contrast media and measurement of the wedged and free hepatic venous pressures. All 11 patients had pulmonary hypertension; three had cor pulmonale only, and the others had combinations of left and right heart failure. In addition, six patients had either a cirrhotic pattern on venography, or portal hypertension. Only three of these six patients had previous clinical evidence of liver disease. This study does not prove that identification of hepatic dysfunction by this method improves the outcome in such patients. However, this low risk modification of standard pulmonary artery catheterization provides additional information which is clinically useful in searching for and avoiding complications of cirrhosis, as well as offering a clearer understanding of pathophysiology in acute multisystem disease.

One-year psychosocial follow-up of patients with chest pain and angiographically normal coronary arteries

As many as 30% of patients with chest pain symptoms who are referred for arteriography are found to have normal coronary arteries. Research has shown that patients with anginal symptoms and normal coronary arteries score higher on neuroticism measurements (anxiety, depression and somatic concerns) at the time of catheterization than patients with anginal symptoms who have coronary artery disease. Research examining the cardiac course of chest pain patients with normal coronary arteries indicates that this is a nonprogressive disorder. Although follow-up studies of these patients report continued chest pain and diminished physical activity, these studies have ignored the psychologic status of the patients. Thus, it is not known whether their higher neuroticism scores at the time of catheterization persist following angiography or whether such elevated indexes of neuroticism are transient phenomena associated with precatheterization anticipatory stress. The present study examined 48 Veterans Administration Medical Center patients: 24 with anginal symptoms and normal coronary arteries and 24 with documented coronary artery disease. The patients completed a structured clinical interview and a set of psychologic inventories on the day before catheterization and 1 year later. The findings established continued high neuroticism scores among patients with anginal symptoms only and supported the findings of other investigators regarding continuing chest pain and restricted physical activity. The knowledge alone of benign coronary artery status resulted in virtually no change in the psychosocial status of these patients. Alternative treatment methods are discussed.

Relationship between Doppler left ventricular diastolic filling indexes and the electrocardiographic criteria for left atrial enlargement

Traditional electrocardiographic (ECG) criteria for left atrial enlargement (LAE) emphasize the increased amplitude and width of the corresponding component of the hypertrophied atrium. Although a correlation exists between LAE and ECG criteria, a cause-and-effect relationship has not been conclusively demonstrated. Because the diastolic properties of the left ventricle directly influence left atrial emptying, these properties might also influence the ECG diagnosis of LAE. Therefore, the authors hypothesized that the ECG criteria for LAE are influenced by diastolic properties of the left ventricle as defined by Doppler-derived parameters.

Usefulness of abnormalities of repolarization in the electrocardiographic diagnosis of healed myocardial infarction

The authors evaluated the ability of criteria involving abnormalities of repolarization to diagnose healed myocardial infarction (MI). They studied the Q, R, S, and T waves and the ST-segments of the electrocardiograms (ECGs) of 60 angiographic-normal patients, 63 patients with angiographic evidence of healed inferior MI, and 33 patients with angiographic evidence of anterior MI. The best individual criteria involving repolarization were T wave amplitude less than or equal to 0.4 mm in lead II for inferior MI (specificity, 93%: sensitivity, 67%) and T wave amplitude greater than 2.4 mm for anterior MI (specificity, 100%: sensitivity, 27%). These T wave criteria enhanced the diagnostic performances of otherwise marginal QRS criteria for both inferior and anterior MI. The authors conclude that ECG criteria that involve abnormalities of the T waves are useful for diagnosing healed MI.

Reevaluation of the VCG and ECG criteria for left ventricular enlargement

Traditional electrocardiographic (ECG) and vectorcardiographic (VCG) criteria for left ventricular enlargement (LVE) understandably emphasize the increased tendency of the maximal electrical forces of ventricular depolarization to be directed toward the left. This tendency is manifested on the ECG by increased amplitudes of the R waves in leads I, AVL, V5 and V6 and by deeper S waves in lead V1. However, because the left ventricle is a relatively posterior as well as leftward structure in the thorax, LVE should also cause these forces to be directed posteriorly. Such changes in the anteroposterior dimension should be reflected in the VCG loop in the transverse plane and in the scalar ECG leads which are placed anterior to the heart. Therefore, we hypothesized that both the ECG and VCG criteria for LVE might be optimized if a variety of parameters that reflect alterations in the anteroposterior as well as in the right to left dimension are investigated.

Recent advances in the diagnosis of myocardial infarction

A method of interpreting ECGs based on vectorcardiographic principles is presented. Using this method, the author and his colleagues have developed improved diagnostic criteria for inferior, anterior, and apical myocardial infarction and challenged the validity of some traditional concepts of electrocardiography.

Nonpenetrating traumatic rupture of the tricuspid valve. Formation of ventricular septal aneurysm and subsequent septal necrosis: recognition by two-dimensional Doppler echocardiography

A 26-year old man was admitted with blunt trauma to the chest following a high-speed deceleration injury. A two-dimensional Doppler echocardiogram demonstrated traumatic rupture of the tricuspid valve and a hematoma in the basilar portion of the interventricular septum. Serial two-dimensional Doppler echocardiographic analyses demonstrated evolutionary formation of a septal aneurysm and subsequent rupture with formation of a ventricular septal defect. The usefulness of the two-dimensional Doppler echocardiogram as a screening tool for cardiac contusion is discussed.

Systemic systolic hypertension in the elderly: correlation of hemodynamics, plasma volume, renin, aldosterone, urinary metanephrines and response to thiazide therapy

Twenty-four men, mean age 63 +/- 1.7 years, with systemic systolic hypertension were studied before and after 1 month of therapy with oral hydrochlorothiazide, 50 mg/day. The control mean plasma volume was 2,664 +/- 96 ml, cardiac index 3.9 +/- 0.2 liters/min/m2, stroke volume index 52 +/- 2 ml/beat/m2, systemic vascular resistance 1,351 +/- 80 dynes s cm-5, plasma aldosterone 8.6 +/- 1.0 ng/dl and 24-hour urinary excretion of metanephrines 0.371 +/- 0.044 mg. On renin-sodium profiling in 23 patients, 12 were classified into a normal group and 11 into a low-renin group; none had high renin values. Based on multiple regression analysis, the 24-hour urinary excretion of total metanephrines appeared to be the single most important factor explaining 28% of the variability in systolic blood pressure (BP). After therapy with oral hydrochlorothiazide, the elevated systolic BP decreased (p less than 0.0001) and diastolic BP decreased (p less than 0.005), with concomitant reduction in systemic vascular resistance (p less than 0.03). Patients in both the normal- and low-renin groups had normal plasma volume and responded similarly to thiazide diuretic therapy, without symptomatic side effects.

Diagnostic significance for coronary artery disease of abnormal Q waves in the "lateral" electrocardiographic leads

To determine the diagnostic significance for coronary artery disease of abnormally large Q waves in leads I, aVL, V5 and V6--the "lateral" electrocardiographic leads--the electrocardiograms of 240 patients who had undergone cardiac catheterization were studied. First, the electrocardiograms of 99 subjects proved normal by cardiac catheterization (group 1) were studied to determine the values of the durations of Q waves in leads I, aVL, V5 and V6 that should be exceeded to be considered abnormal. These values were 30, 30, 20 and 25 ms, respectively. Then, 67 patients were identified who had abnormal Q waves in at least 1 of these leads (group 2) and 74 patients with at least 1 angiographic abnormality but without abnormal Q waves in any of these leads (group 3). Group 2 had generally more extensive left ventricular disease and a higher prevalence of anterior, inferior and apical healed myocardial infarction (MI) than group 3. However, compared with group 3, group 2 had lower prevalences of significant narrowing of the coronary arteries that supply the left ventricular lateral wall. Within group 2, abnormal Q waves in leads I and aVL (traditionally designated high lateral MI) were associated with anterior as well as apical MI, and abnormal Q waves in leads V5 and V6 (traditionally designated anterolateral MI) were associated with inferior as well as apical MI. Thus, abnormal Q waves in leads I, aVL, V5 and V6 tend to reflect apical rather than lateral MI and the term anterolateral MI is especially misleading.

The effect of nitroglycerin on forearm arterial distensibility

Nitroglycerin acts, in part, to reduce arterial impedance, and thus left ventricular work. The reduction in arterial impedance is largely attributable to a fall in systemic vascular resistance, but may also be due to an increased distensibility of the arterial tree. In this study, volume distensibility of forearm arteries was calculated from measurements of pulse-wave velocity before and during intravenous nitroglycerin infusion. Since a fall in blood pressure itself increases arterial distensibility, the induced blood pressure change was controlled as a variable by repeating the measurements with the subject's forearm in a plastic cylinder and repeating the measurements at a variety of altered cylinder pressures. At every studied pressure, nitroglycerin infusion increased forearm arterial distensibility, demonstrating another way in which nitroglycerin reduces left ventricular afterload. Since the pulsatile portion of cardiac work is approximately 10% of total work, the magnitude of this nitroglycerin effect on cardiac function is probably small.

Importance of the distance and velocity of electrical forces in the diagnosis of inferior wall healed myocardial infarction: a vectorcardiographic study

The vectorcardiograms of 41 patients with angiographically proved inferior myocardial infarction (MI) and 51 normal subjects were analyzed to determine whether it is the time (in milliseconds) or the distance (in millivolts) of the initial superiority directed forces of ventricular depolarization that is increased more by inferior MI, and whether parameters derived from both the initial superior time and distance can be used to detect inferior MI. The 10 best individual and the 10 best paired criteria for inferior MI involve superior distance, either alone or used in the calculation of average velocity (in volts per second), and the product of initial superior time and distance (in millivolts per second). The 2 best individual criteria for inferior MI are: inferior velocity more than 0.0065 V/s (sensitivity 71%, specificity 100%) and superior distance more than 0.39 mV (sensitivity 68%, specificity 100%). These diagnostic performances are superior to those of the best criterion that involves only the duration of the initial superior forces, i.e., initial superior time longer than 28 ms (sensitivity 49%, specificity 98%) (chi 2 = 8.42, p less than 0.005 and chi 2 = 6.31, p less than 0.025, respectively). Initial superior distance and parameters calculated from both initial superior distance and time are better vectorcardiographic criteria for inferior MI than are criteria that involve only initial superior time.

Importance of the terminal portion of the QRS in the electrocardiographic diagnosis of inferior myocardial infarction

The scalar electrocardiograms of 64 patients with inferior wall myocardial infarction (MI) and 87 normal subjects were quantitatively analyzed to determine the respective contributions of the initial and terminal portions of the QRS to the diagnosis of inferior MI. Of the 10 best individual electrocardiographic criteria for inferior MI, 7 were Q-wave criteria and 3 were criteria that consisted of delayed termination of the QRS in leads II or III. Combining the best terminal QRS criterion (the QRS in lead III ending at least 20 ms later than the QRS in lead I) with the 7 best Q-wave criteria and the best Q-wave criterion (Q wave 40 ms or longer in lead aVF) with the 3 best terminal QRS criteria, resulted in criteria with better sensitivities and overall diagnostic performances than those of the individual criteria. Analyzing the vectorcardiograms that were also available in 26 of the patients with inferior MI and 34 of the normal subjects showed that the delayed inscription of the end of the QRS in leads II and III in patients with inferior MI is due to redirection of the terminal forces of ventricular depolarization. The terminal portions of the QRS complexes in the limb leads, considered both alone and in conjunction with traditional measurements of Q waves, contain information that is useful for diagnosing inferior MI.

Comparison of optimal scalar electrocardiographic, orthogonal electrocardiographic and vectorcardiographic criteria for diagnosing inferior and anterior myocardial infarction

A scalar electrocardiogram (ECG), orthogonal ECG and vectorcardiogram (VCG) were recorded in 46 normal persons, 38 patients with inferior myocardial infarction (MI) and 22 patients with anterior MI proved at cardiac catheterization. The diagnostic information provided by the scalar ECG, orthogonal ECG and VCG was quantitatively analyzed and the optimal criteria for diagnosing inferior and anterior MI exhibited by each method were identified. The optimal scalar electrocardiographic, orthogonal electrocardiographic and vectorcardiographic criteria, respectively, are: For inferior MI: initial superior duration in lead aVF greater than 30 ms (sensitivity 63%, specificity 100%), superior/inferior amplitude ratio in lead Y greater than or equal to 0.2 (sensitivity 63%, specificity 96%), initial superior duration greater than 29 ms or initial superior distance greater than 0.4 mV in the frontal plane loop (sensitivity 68%, specificity 100%). For anterior MI: initial anterior duration in lead V2 less than 20 ms or initial anterior duration in lead V3 less than 25 ms (sensitivity 91%, specificity 100%), anterior/posterior duration ratio in lead Z less than 0.3 (sensitivity 73%, specificity 98%), initial anterior duration less than 15 ms in the transverse plane loop (sensitivity 64%, specificity 98%). There were no significant differences among the performances of the optimal scalar ECG, orthogonal ECG and the VCG for diagnosing inferior MI. However, the performance of the optimal scalar ECG was superior to that of the optimal orthogonal ECG and the optimal VCG for diagnosing anterior MI (chi-square = 5.20, p less than 0.02 and chi-square = 7.14, p greater than 0.01, respectively).

Electrocardiographic criteria for the diagnosis of anterior myocardial infarction: importance of the duration of precordial R waves

A systematic evaluation of a large number of electrocardiographic (ECG) variables that might be useful for diagnosing anterior myocardial infarction (MI) is reported. Previous anterior MI was shown to be present or absent by cardiac catheterization in 199 patients. The best discriminator between cases and noncases of anterior MI in most patients is the presence of a Q wave of any magnitude or an initial R wave less than 20 ms in lead V2. In patients with ECG evidence of associated left ventricular or type C right ventricular enlargement, the more stringent criterion of a Q wave of any magnitude in lead V2 yielded the optimal combination of sensitivity and specificity for diagnosing anterior MI. The diagnostic performance of the proposed criteria for anterior MI is superior to that of more traditional criteria that use measurements of the absolute and relative amplitudes of precordial R waves.

Effect of age on arterial distensibility in Asymptomatic humans

This report describes a noninvasive method by which the volume distensibility of forearm arteries can be calculated from direct measurements of pulse wave velocity. Such measurements are made at a variety of transmural arterial pressures (TMP) accomplished by placing the forearm in a cylinder and changing the pressures within. This technique eliminates arterial blood pressure as a variable, which strongly influences arterial distensibility. We studied 48 asymptomatic men and women, ages 21 to 98 years. There was considerable scatter, but significant positive relationships were demonstrated between increasing arterial distensibility and age at ambient and lower TMPs. This finding can be explained by an age-related reduction in arterial luminal diameter and an increase in arterial wall thickness which reduces arterial wall tension and more than offsets the increased stiffness produced by changes in wall composition. In six subjects, pulse tracings were simultaneously recorded on paper and analog tape. The taped curves were digitized and subjected to Fourier analysis to determine the wave velocity of individual harmonics. The characteristic wave velocity was defined and found comparable to the hand method used in the same beats (regression coefficient = + 0.97). These data indicate that the automatic and manual methods measured the same variable.

Improved electrocardiographic criteria for the diagnosis of left anterior hemiblock

New electrocardiographic (ECG) criteria for the diagnosis of left anterior hemiblock are proposed. The proposed criteria are based upon the relation between portions of the vectorcardiographic (VCG) QRS loop in the frontal plane and the corresponding portions of the ECG QRS complexes recorded by the limb leads. The application of the proposed criteria requires that the tracings be obtained with 3-channel ECG machines so that the temporal relation between the QRS complexes in simultaneously recorded limb leads can be inspected. This type of analysis of the electrocardiogram permits prediction of features of the VCG QRS loop that are important for the diagnosis of left anterior hemiblock. The proposed ECG criteria for the diagnosis of left anterior hemiblock are (1) the QRS complexes in leads aVR and aVL each end in an R wave (terminal R wave), and (2) the peak of the terminal R wave in lead aVR occurs later than the peak of the terminal R wave in lead aVL. The sensitivity and specificity of the proposed criteria were empirically evaluated using series of electrocardiograms obtained under clinical circumstances during which the occurrence of left anterior hemiblock was, respectively, likely and unlikely. The performance of the proposed criteria was statistically superior to that of 2 sets of frontal plane QRS axis criteria.

Electrocardiographic criteria for the diagnosis of combined inferior myocardial infarction and left anterior hemiblock

New electrocardiographic (ECG) criteria for diagnosing the combination of inferior myocardial infarction and left anterior hemiblock are proposed. The proposed criteria are based upon the relations between portions of the vectorcardiographic QRS loop in the frontal plane and the corresponding portions of the QRS complexes recorded by the limb leads. The application of the proposed criteria requires that the tracings be obtained with 3-channel ECG machines. The proposed criteria for the diagnosis of inferior myocardial infarction and left anterior hemiblock are as follows: (1) leads aVR and aVL both end in R waves, with the peak of the terminal R wave in lead aVR occurring later than the peak of the terminal R wave in lead aVL, and (2) a Q wave of any magnitude is present in lead II. The performance of the proposed criteria was superior to that of 10 combinations of traditional ECG criteria for inferior myocardial infarction and left anterior hemiblock.

Distribution of Vibrio vulnificus and other lactose-fermenting vibrios in the marine environment

During the summer of 1981, 3,887 sucrose-negative vibrios were isolated from seawater, sediment, plankton, and animal samples taken from 80 sites from Miami, Fla., to Portland, Maine. Of these, 4.2% were able to ferment lactose. The lactose-positive strains isolated from the various samples correlated positively with pH and turbidity of the water, vibrios in the sediment and oysters, and total bacterial counts in oysters. Negative correlations were obtained for water salinity. Numerical taxonomy was performed on 95 of the lactose-fermenting environmental isolates and 23 reference strains. Five clusters resulted, with the major cluster containing 33 of the environmental isolates and all of the Vibrio vulnificus reference strains. The 33 isolates, which produced an acid reaction in lactose broth within hours of initial inoculation, represented 20% of all lactose-fermenting vibrios studied. These isolates were nearly identical phenotypically to clinical strains of V. vulnificus studied by the Centers for Disease Control, Atlanta, Ga., and by our laboratory, and their identification was confirmed by DNA-DNA hybridization studies. V. vulnificus was isolated from all sample types and from Miami to Cape Cod, Mass., and comparison of the environmental parameters of the eight subsites yielding this species with those of all 80 subsites revealed no significant differences. The majority of the isolates were obtained from animals, with clams providing most (84%) of these. On injection into mice, 82% of the V. vulnificus isolates resulted in death. Members of the remaining four clusters contained strains which differed from V. vulnificus in such phenotypic traits as luminescence and in urease or H(2)S production. None of the other reference cultures, including nine other Vibrio species, were contained in the remaining clusters, and these isolates could not be identified. Most of these were also lethal for mice. Phenotypic differences, potential pathogenicity, and geographic distribution of the five clusters were examined. It is concluded that V. vulnificus is a ubiquitous organism, both geographically and in a variety of environmental sources, although it occurs in relatively low numbers. The public health significance of this organism and of the other unidentified lactose-fermenting Vibrio species is discussed.

Distribution and ecology of Vibrio vulnificus and other lactose-fermenting marine vibrios in coastal waters of the southeastern United States

Water, sediment, plankton, and animal samples from five coastal sites from North Carolina to Georgia were sampled for their lactose-fermenting vibrio populations. Over 20% of all vibrios tested were sucrose negative and o-nitrophenyl-beta-D-galactopyranoside (ONPG) positive, suggesting identification as the human pathogen Vibrio vulnificus. These vibrios were isolated from all sample sites and sources (water, sediment, plankton, and animals). Correlations with several of 19 environmental parameters monitored at each site were found for total vibrios. The presence of ONPG-positive, sucrose-negative vibrios was correlated with hydrocarbon levels in the water and, in the case of plankton samples, with salinity. A total of 279 sucrose-negative, ONPG-positive isolates were subjected to numerical taxonomic analysis, which resulted in three major clusters. Cluster I corresponded to and included 11 reference strains of V. vulnificus. Cluster II contained the largest number (133) of isolates, of which the great majority were bioluminescent. Although having a resemblance to V. harveyi, the isolates were ONPG positive and many were H2S positive. Cluster III consisted of strains similar to the group F vibrios (V. fluvialis). Of all of the isolates, 55% were luminescent, of which over 20% were lethal when injected into mice. Problems involved in detecting lactose fermentation among marine vibrios and the potential pathogenicity of these organisms are discussed.

Detection of experimental right ventricular necrosis using vectorcardiograms obtained during artificial pacing

This study was carried out to evaluate the possible usefulness of the VCG obtained during right ventricular pacing in the diagnosis of right ventricular necrosis. Myocardial necrosis was produced by injecting 40% formalin into the ventricular walls of 18 open-chest mongrel dogs. The injections were made in the inferior wall of the left ventricle in nine dogs (Group A) and in the inferior wall of the right ventricle in the remaining nine dogs (Group B). Analysis of vectorcardiographic QRS loops obtained during artificial pacing of the right ventricular apex was made before and 60 minutes after the injections. In Group B, but not in Group A, the injections resulted in superior displacement of initial QRS forces as indicated by measurements of time, distance, amplitude and angle. The pacing VCG, performed in serial fashion, is a specific and sensitive means of detecting right ventricular inferior wall necrosis in the experimental animal. Application of these findings to the diagnosis of myocardial infarction in humans requires further investigation.

Vectorcardiographic manifestations of experimental right ventricular necrosis

This study was carried out to evaluate the possible usefulness of the VCG in the diagnosis of right ventricular necrosis. Myocardial necrosis was produced by injecting 40% formalin into the ventricular walls of 21 open-chest mongrel dogs. The injections were made in the inferior wall of the left ventricle in eight dogs (Group A) and in the inferior wall of the right ventricle in 13 dogs (Group B). Analysis of vectorcardiographic QRS loops obtained before and two hours after the injections revealed that both left and right ventricular necrosis resulted in a decrease in: maximum inferior amplitude, inferior amplitude at 10 and 20 msec. and maximum frontal plane angle. In Group A, six dogs had counterclockwise initial forces in the frontal plane before the injections and these became clockwise following the injections. In Group B, nine dogs had counterclockwise initial forces in the frontal plane before the injections and these remained counterclockwise following the injections. The only consistent QRS change in scalar ECGs that occurred after the injections was the development of small Q waves in the six dogs in Group A that manifested clockwise initial forces in the frontal plane. The VCG performed in serial fashion may be more sensitive than the 12 lead ECG for detecting right ventricular inferior wall necrosis in the experimental animal. Application of these findings to the diagnosis of myocardial infarction in humans requires further investigation.

Improvement in arterial oxygenation by saralasin infusion in man

Simultaneous hemodynamic and blood gas measurements were performed in 26 hypertensive adults, who were cigarette smokers, before and after a 30-minute infusion of saralasin (5 microgram/kg/min) which is a highly specific competitive antagonist of angiotensin II (AII). The arterial pressure fell in nine, rose in seven and was unchanged in ten patients. The mean cardiac index for the entire group remained unchanged. Pulmonary arterial or wedge pressure, pulmonary vascular resistance, arterial PCO2 and pH did not change. Unrelated to the hemodynamic changes, the mean arterial oxygen pressure (PaO2) increased from 68.6 +/- 2.2 mm Hg to 73.9 +/- 2.1 mm Hg (P less than 0.001). In the absence of a significant increase in alveolar ventilation as indicated by an unchanged mean PCO2 and lacking a hemodynamic explanation, the mechanism for the rise in PaO2 is speculative at this stage. The possibility of an improvement in the distribution of ventilataion by saralasin infusion is under investigation.

Effects of sublingual nitroglycerin on resting pulmonary gas exchange and hemodynamics in man

Simultaneous hemodynamic, ventilation and blood gas measurements were performed in 19 males during cardiac catheterization for evaluation of chest pain syndrome before and 3 to 5 min after 0.4 mg sublingual nitroglycerin. Pulmonary arterial pressures and total pulmonary vascular resistance fell (P less than 0.001 for both), and mean systemic arterial pressure decreased (P less than 0.05). However, peripheral vascular resistance, cardiac output, and mixed venous PO2 did not change. Total and tidal ventilation, PCO2, pH, and base excess remained unchanged. However, the arterial PO2 decreased from a mean of 80 +/- 3 (SEM) to 72 +/- 2 mm Hg (P less than 0.001) and mean venous admixture increased from 8.8 +/- 1% to 12.6 +/- 1.5% (P less than 0.001). The alveolar arterial PO2 difference increased (P less than 0.001) and the dead space tidal volume ratio rose (P less than 0.05). We conclude that the decrease in arterial PO2 following sublingual nitroglycerin is caused by redistribution of pulmonary blood flow with imbalance in ventilation-perfusion relationships or shunting.

Hemodynamic, ventilatory and blood gas changes during infusion of sodium nitroferricyanide (nitroprusside). Studies in patients with congestive heart failure

Simultaneous hemodynamic, ventilatory, and blood gas studies were performed in 16 men with congestive heart failure before and during infusion of sodium nitroferricyanide (nitroprusside). The cardiac index increased from 2.00+/-0.16 L/min/sq m (SE) to 2.38+/-0.14 L/min/sq m, and the total pulmonary and systemic peripheral resistances fell from 928+/-123 to 494+/-57 dynes sec cm-5 and from 2,208+/-210 to 1,558+/-121 dynes sec cm-5, respectively. Both systemic and pulmonary arterial decreased during infusion of sodium nitroferricyanide, and the mixed venous oxygen pressure increased. There was no change in total or alveolar ventilation, arterial carbon dioxide tension, pH, or base excess; however, the mean arterial oxygen pressure (PaO2) decreased from 74+/-3 mm Hg to 68+/-3 mm Hg and the venous admixture effect increased from 8+/-1% to 13+/-2%. We conclude that the decrease in PaO2 during infusion of sodium nitroferricyanide resulted from a worsening of the ventilation-perfusion relationships due to increased perfusion of underventilated pulmonary units.

Treatment of acute aortic insufficiency with sodium nitroferricyanide. Documentation of beneficial effect by noninvasive means

The findings in a patient with acute aortic insufficiency who was treated with sodium nitroferricyanide (sodium nitroprusside) prior to aortic valve replacement are presented. Administration of the drug resulted in clinical improvement, which was reflected in changes in systemic and pulmonary arterial pressures and in noninvasive measurements. Sodium nitroferricyanide is useful in the management of patients with severe acute aortic insufficiency, and its effect may be monitored by noninvasive means.