bluuebunny/crossref_metadata_2025 huggingface dataset:
Two periods of early ventricular arrhythmia in the canine acute myocardial infarction model.
Authors: Kaplinsky E , Ogawa S , Balke C W , Dreifus L S
Published: June 2012

The time course of ventricular arrhythmias in the early period (0--30 minutes) after ligation of the left anterior descending coronary artery was studied in 41 open-chest mongrel dogs anesthetized with pentobarbital sodium (Nembutal). ECGs and seven single and composite electrograms from various regions in and around the ischemic zone were recorded throughout the experiments. Two periods of ventricular arrhythmias were clearly seen. The first occurred 2--10 minutes after coronary ligation, peaking at 5--6 minutes, and was designated as immediate ventricular arrhythmias (IVAs). There was a distinct correlation between incidence, severity, onset and termination of IVA and the degree of local delay and fragmentation of the normal sinus activation spread in the ischemic subepicardial zone. The second wave of ventricular arrhythmias occurred 12--30 minutes after ligation independently of the previous increased delay and fragmentation of activation in the ischemic subepicardium. Delayed ventricular arrhythmias (DVAs) were as severe as IVAs--there were nine instances of ventricular fibrillation during DVA and seven during IVA. While the mechanism of IVA is most probably related to reentry accompanied by delay and fragmentation of ischemic subepicardial activation, the mechanism of DVA remains unclear. Our evidence suggests that DVAs are also reentrant, with the reentry pathways located in deep myocardial structures or involving microscopic pathways at the Purkinje muscle junction.
Noninvasive recording of His-Purkinje activity in patients with complete atrioventricular block. Clinical application of an "automated discrimination circuit".
Authors: Takeda H , Kitamura K , Takanashi T , Tokuoka T , Hamamoto H , Katoh T , Niki I , Hishimoto Y
Published: June 2012

In seven patients with complete atrioventricular (AV) block, His bundle electrograms (HBEs), standard ECG recordings, bipolar esophageal ECGs and highly amplified, filtered, bipolar chest lead ECGs were simultaneously recorded. The filtered chest lead ECG was averaged to determine His-Purkinje activity (HPA). A simplified device, the "automated discrimination circuit," was used to selectively eliminate the superimposed atrial and ventricular potentials that are characteristic of complete AV block and unsuitable for signal averaging. The processed chest lead ECG was amenable to conventional techniques of signal averaging. In four patients with block proximal to the AV node diagnosed by HBE, there was no activity after the P wave in the surface-averaged ECGs. HPA was consistently recorded before the QRS in the surface-averaged ECG. The measurements of the HV and HPA-V intervals were very close, with a difference of less than 2 msec. Three patients with block distal to the His bundle by HBE showed a loss of electrical potential before the QRS in the surface-averaged ECG, but had a consistent HPA after the P waves. The P-HPA intervals coincided well with PH intervals, with a maximal difference of 5 msec.
A new cardiac prosthesis: the St. Jude Medical cardiac valve: in vivo results.
Authors: Emery R W , Mettler E , Nicoloff D M
Published: June 2012

The St. Jude Medical cardiac valve prosthesis is a low profile, lightweight, bi-leaflet, central-flow device constructed entirely of pyrolytic carbon. In vivo testing was performed in 24 cows in which the tricuspid valve (n = 14) or mitral valve (n = 10) was replaced by a St. Jude Medical prosthesis with a 26 mm tissue annulus diameter. Eight animals died in the operative period. The 16 surviving animals were sacrificed at 4, 8, 12, or 18 weeks. There were no valve-related deaths nor mechanical valve failures. Anticoagulation was not used in the postoperative period during which time monthly laboratory parameters were obtained including hemoglobin, hematocrit, white cell count, red cell count and indices, lactic acid dehydrogenase, serum haptoglobin, and, additionally at sacrifice, platelet and red cell morphology. Values indicated this prosthesis did not cause hemolysis. At sacrifice the pulmonary arterial tree and peripheral organs showed no evidence of thromboemboli. There was smooth endocardial ingrowth on all valve sewing rings. One valve had thrombus formation on the valve sewing ring. Nine animals were anesthetized prior to sacrifice and underwent open cardiac catheterization. Ventriculography (n = 6) showed minimal transvalvar reflux, and atriograms (n = 6) demonstrated central flow. Transvalvar gradients were 0 to 22 mm Hg (n = 9). One valve of an 18-week tricuspid implant was examined for wear; valve life was calculated to be greater than 2500 years. These data in conjunction with in vitro test results justify clinical trial of the St. Jude Medical prosthesis.
Safe early revascularization for continuing ischemia after acute myocardial infarction.
Authors: Levine F H , Gold H K , Leinbach R C , Daggett W M , Austen W G , Buckley M J
Published: June 2012

Early revascularization following myocardial infarction (MI) is reported to have a high risk of extension of and hemorrhage into infarction with resulting high mortality and morbidity. To evaluate this issue, 80 post-MI patients (aged 32-74 years) with unstable angina pectoris resistant to maximal medical therapy were reviewed. All patients underwent early uncomplicated angiography and subsequent revascularization; 55 (69%) were less than 10 days post-MI, and 25 (31%) were 10-30 days post-MI. Intraaortic balloon pumping was required in 72% for relief of intractable angina or hemodynamic instability. Of the 80 patients, 19% had single vessel disease (VD), 31% double VD, and 50% triple VD. The mortality rate from coronary bypass surgery was 7/80 (8.8%), with four cardiac and three noncardiac deaths. Two patients suffered a perioperative MI (2.5%). At a mean follow-up period of 33 months, there had been only one late death and one recurrent nonfatal MI; 96% of the patients had no significant angina. In patients with continuing ischemia immediately after MI, myocardial revascularization can be safely performed without further injury to the myocardium, and with excellent long-term results.
Primary clinical experience with the Hall-Kaster valve in the aortic position: results at 3 months including hemodynamic studies.
Authors: Nitter-Hauge S , Enge I , Sembe B K , Hall K V
Published: June 2012

The Hall-Kaster pivotal disc prosthetic heart valve was introduced in 1977. The primary goal of the design was to obtain the least possible obstruction to flow. Toward this end, innovations in the tilting axis, disc guidance mechanisms, and disc translational freedom combine to improve flow through both orifice segments of the open valve. The present study reports the primary clinical and hemodynamic findings in 28 patients (mean age, 53.8 years) with aortic valve disease, examined 3 months after insertion of the Hall-Kaster pivotal disc valve. The hemodynamics findings displayed low gradients and high calculated orifice areas. Satisfactory flow was observed through both the major and minor openings of the prosthesis. There were no arterial thromboembolic episodes. The increase in serum lactate dehydrogenase activity was moderate, indicating a slight-to-moderate intravascular haemolysis.
Preoperative evaluation of subvalular fibrosis in mitral stenosis. A predictor factor in conservative vs replacement surgical therapy.
Authors: Akins C W , Kirklin J K , Block P C , Buckley M J , Austen W G
Published: June 2012

To assess the degree of mitral subvalvular fibrosis (SVF) in patients with mitral stenosis, left ventriculograms were reviewed, and a mitral subvalvular distance ratio (DR) was determined by dividing the distance from the papillary muscle tips to the closed mitral leaflets in systole by the distance from the aortic valve to the left ventricular apex in diastole. In 15 patients with normal ventricles, the mean DR was 0.244 +/- 0.017. In nine patients with minimal SVF, the mean DR was 0.181 +/- 0.025. In 10 patients with moderate SVF, the mean DR was 0.148 +/- 0.033. In 5 patients with severe SVF, the mean DR was 0.087 +/- 0.009. All mean DRs were mutually distinguishable at p less than 0.01. The clinical results and preoperative DR of 28 patients who had mitral commissurotomy were reviewed. A DR of less than 0.140 precluded a good longterm result from mitral commissurotomy alone. The DR reliably predicts the degree of SVF preoperatively and identifies patients with mitral stenosis who require valve replacement or a direct surgical attack on the subvalvular mechanism.
Late hemodynamic evaluation of Hancock Modified orifice aortic bioprosthesis.
Authors: Craver J M , King S B , Douglas J S , Franch R H , Jones E L , Morris D C , Kopchak J , Hatcher C R
Published: June 2012

Nineteen patients with Hancock Modified Orifice prosthesis (HMO-250), size 19 to 23 mm, were recatheterized 6 to 16 months following aortic valve replacement (AVR). Although hemodynamic characteristics varied widely, HMO-250 compared favorably to the standard model 243 (less than 0.05). Mean peak resting gradient across HMO-250 was 14.8 torr at rest and rose to 26.8 torr with exercise. Systolic gradients for HMO-250, both resting and exercise, were improved for 21 mm (p less than 0.01), but not for 23 mm. Increasing the patient's body surface area (BSA) correlated with increasing gradients for 23 mm (p less than 0.05), but was unrelated to 21 mm. Effective orifice areas were similarly found to be improved with 21 mm HMO-250 but unchanged for 23 mm. Use of the 21 or 23 mm size HMO for AVR is supported only when the patient's body surface area is less than 1.8 m2. If the body surface area is greater than 1.8 m2, annulus enlargement and a larger size bioprosthesis should be employed. Use of 19 mm porcine xenograft for AVR is not supported.
An important complication of Hancock mitral valve replacement in children.
Authors: Kutsche L M , Oyer P , Shumway N , Baum D
Published: June 2012

Nine children ages 2--15 years have undergone mitral valve replacement (MVR) with Hancock porcine heterograft valves for severe mitral insufficiency. The etiology of the mitral valve disease was rheumatic in two patients, and congenital in seven. Porcine valve sizes ranged from 19--31 mm. Follow-up has been from 1.6 to 6.1 years (mean, 4.3 years). All nine children have had marked postoperative improvement, no thromboembolic complications despite no long-term anticoagulations, and no episodes of endocarditis. There have been no early or late deaths. Although six of the nine patients remain asymptomatic, three others developed severe fibrocalcific obstruction of the heterograft, requiring valve re-replacement at 3.5, 3.6, and 4.8 years following the initial valve replacement. This complication has not been previously reported in children. It is a factor that must be considered when deciding on MVR for children and their postoperative management.
Second-degree atrioventricular block.
Authors: Zipes D P
Published: June 2012

1) While it is possible only one type of second-degree AV block exists electrophysiologically, the available data do not justify such a conclusion and it would seem more appropriate to remain a "splitter," and advocate separation and definition of multiple mechanisms, than to be a "lumper," and embrace a unitary concept. 2) The clinical classification of type I and type II AV block, based on present scalar electrocardiographic criteria, for the most part accurately differentiates clinically important categories of patients. Such a classification is descriptive, but serves a useful function and should be preserved, taking into account the caveats mentioned above. The site of block generally determines the clinical course for the patient. For most examples of AV block, the type I and type II classification in present use is based on the site of block. Because block in the His-Purkinje system is preceded by small or nonmeasurable increments, it is called type II AV block; but the very fact that it is preceded by small increments is because it occurs in the His-Purkinje system. Similar logic can be applied to type I AV block in the AV node. Exceptions do occur. If the site of AV block cannot be distinguished with certainity from the scalar ECG, an electrophysiologic study will generally reveal the answer.
Atherogenesis: a postprandial phenomenon.
Authors: Zilversmit D B
Published: June 2012

The hypothesis that plasma chylomicrons in persons who ingest a cholesterol-rich diet are atherogenic is evaluated. Evidence is presented that in humans, and experimental animals, chylomicron remnants as well as low-density lipoproteins are taken up by arterial cells. In persons who do not have familial hyperlipoproteinemia, atherogenesis may occur during the postprandial period. Research directions that may contribute to the evaluation of chylomicron remnants as a risk factor for atherogenesis are discussed. Lipoprotein studies after administration of a test meal containing fat and cholesterol are urgently needed.
The influence of left ventricular late diastolic filling on the A wave of the left ventricular pressure trace.
Authors: Ambrose J A , Teichholz L E , Meller J , Weintraub W , Pichard A D , Smith H , Martinez E E , Herman M V
Published: June 2012

To study the influence of left ventricular (LV) late diastolic filling on the A wave of the LV pressure, simultaneously recorded echocardiographic LV dimensions and high-fidelity LV pressure measurements were taken in 24 patients. Group 1 comprised eight patients without LV hypertrophy (LVH) and LV end-diastolic pressure (LVEDP) less than or equal to 13 mm Hg. Group 2 comprised 16 patients with LVH secondary to aortic stenosis, idiopathic hypertrophic subaortic stenosis, or hypertension and increased LVEDP. Patients in group 2 had significantly thicker left ventricles, decreased mitral E-to-F slopes, and larger A waves in the LV pressure curve. On the basis of end-diastolic chamber stiffness, we divided group 2 into two populations: 12 patients (group 2A) with end-diastolic chamber stiffness similar to that in group 1, and four patients (group 2B) with markedly elevated end-diastolic chamber stiffness. Patients in group 2A had a larger atrial contribution to LV filling than those with markedly abnormal stiffness (group 2B). Therefore, in LVH an increased A wave in the LV pressure may be related to either elevated end-diastolic chamber stiffness or augmented left atrial volume transport.
Left ventricular volumes by gated equilibrium radionuclide angiography: a new method.
Authors: Slutsky R , Karliner J , Ricci D , Kaiser R , Pfisterer M , Gordon D , Peterson K , Ashburn W
Published: June 2012

To compare radionuclide end-diastolic (EDV) and end-systolic (ESV) volumes with angiographic volume, we studied 52 patients with equilibrium radionuclide angiography using 99mTc-human serum albumin within 48 hours of contrast angiography. Each RR interval was divided into 20--28 equally timed frames and a time-activity curve generated. End-diastolic counts were taken at the early peak of the curve and end-systolic counts at its nadir. Counts were divided by the total number of processed heart beats and normalized for: 1) dose per body surface area; 2) plasma volume; and 3) counts/ml of plasma. A cardiac phantom was developed and serial volumes were studied using a normalization factor. Radionuclide values were expressed as dimensionless units and compared with either biplane angiographic volumes (in the patient studies) or known phantom volumes. Good correlations were obtained with methods 1 and 2 in 35 patients (r greater than 0.84), but the best correlation was obtained in 17 patients when normalization for counts/ml of plasma was used (r = 0.98; y = 0.255 x -0.121). The standard error of the estimate (SEE) was +/- 11.5 ml for EDV and +/- 7.3 ml for ESV. The phantom study also showed an excellent correlation (r = 0.99), with a SEE of +/- 6.5 ml. We conclude that a radionuclide method independent of geometric assumptions can be used to estimate left ventricular volume in man.
Exercise-induced ST elevation in patients without myocardial infarction.
Authors: Longhurst J C , Kraus W L
Published: June 2012

A review of 6040 consecutive exercise tests yielded 106 patients without previous myocardial infarction (MI) who had exercise-induced ST elevation (greater than or equal to 0.5 mm in a 15-lead ECG system). In 46, ST elevation was correlated with left ventriculography and coronary angiography. Coronary artery disease (CAD) (greater than or equal to 70% narrowing) was detected in 40 of 46 patients: 12 patients had one-vessel disease, 13 had two-vessel disease, and 15 had three-vessel disease. Resting ventriculograms were normal in 36 of 40 patients. Of 21 patients with anterior (V1-V3) ST elevation, 86% had a left anterior descending (LAD) obstruction and 78% had obstruction proximal to the first diagonal branch. LAD disease occurred significantly more frequently than right and circumflex CAD. There was no anatomic correlation of three persons with lateral (leads V4--6, I or aVL) or 27 patients with inferior-posterior (leads II, III, aVF, Y or Z) exercise-induced ST elevation. Therefore, exercise-induced ST elevation is strongly correlated with CAD but not resting wall motion abnormalities. Further, anterior exercise-induced ST elevation in patients without a previous MI often predicts a significant proximal LAD obstruction.
Noninvasive screening criteria for enhanced 4-year survival after aortocoronary bypass surgery.
Authors: Bruce R A , DeRouen T A , Hammermeister K E
Published: June 2012

Two thousand one men with coronary heart disease (CHD) who were enrolled in the Exercise Testing Registry of the Seattle Heart Watch had symptom-limited maximal exercise tests at the initial clinical examination and follow-up surveillance of subsequent mortality for 4.1 +/- 1.6 years. When subdivided into three mutually exclusive subgroups, 636 patients did not have exertional myocardial ischemia, left ventricular dysfunction or cardiomegaly; 885 without cardiomegaly had only exertional ischemia; 480 had left ventricular dysfunction by either cardiomegaly and/or two noninvasive exertional criteria, with or without exertional myocardial ischemia. Three hundred thirty-one men had aortocoronary bypass surgery, while 1670 remained unopened for at least 4 years. Only 34% of the operated patients who had left ventricular dysfunction, as defined, showed a marked improvement in 4-year survival rates (p less than 0.01). Differences in the annual CHD mortality rates in relation to surgical treatment in the other two groups were not statistically significant. Restricting the analysis to a subset of patients who had invasive studies did not alter the conclusion. Accordingly, we suggest the use of noninvasive criteria to aid preliminary screening of patients for invasive studies and surgical treatment.
Atrial flutter with exit block.
Authors: Homcy C J , Lorell B , Yurchak P M
Published: June 2012

The mechanism of atrial flutter is controversial. A 76-year-old woman with rheumatic heart disease was referred to our clinic with an unusual rhythm disturbance which initially appeared to be classic atrial flutter at a rate of 300 beats/min. Later tracings, however, demonstrated a rate exactly one-half that of the earlier ECGs, with an identical p-wave morphology and vector. This latter rhythm also behaved in a manner expected for a flutter mechanism in that both spontaneously and with carotid pressure high-degree atrioventricular block occurred without alteration of the underlying atrial mechanism. Finally, the two rates interchanged spontaneously over several days without any significant interval changes in medical therapy. These findings were initially explained as probable digoxin toxicity. The underlying mechanism, however, was more likely atrial flutter with exit block and in this patient may have represented another facet of her sick sinus syndrome. This unusual phenomenon is discussed in terms of previous reports and possible implications for the mechanism of atrial flutter.
Epicardial mapping and electrocardiographic models of myocardial ischemic injury.
Authors: Smith G T , Geary G , Ruf W , Roelofs T H , McNamara J J
Published: June 2012

The amplitude and distribution of epicardial ST-segment elevation (ST) were examined for an 8-hour period after coronary occlusion in eight baboons and five pigs. ST was determined from unipolar epicardial electrograms obtained from a high-resolution matrix of fixed electrodes overlying a transmural region of ischemia. A relatively uniform degree of ST was observed overlying the ischemic region for 20 minutes after coronary occlusion. A gradient in ST from the periphery to the center of the ischemic region was documented after 20 minutes of ischemia. In 10 other pigs, change in the degree of ST was examined contingent on either an increase (five pigs) or decrease (five pigs) in the size of the ischemic region after 1 hour of preexisting ischemia. An abrupt increase in the number of electrodes that showed ST (NST) from 7.8 +/- 1.24 (SEM) to 14.8 +/- 1.35 (90%) was associated with an increase in mean ST of 58% from 4.28 +/- 0.61 mV to 6.78 +/- 0.84 (p less than 0.05). An abrupt decrease in NST from 25.2 +/- 2.63 to 14.6 +/- 2.22 (42%) was associated with a decrease in mean ST of 24%, from 8.2 +/- 0.36 mV to 6.3 +/- 0.30 mV (p less than 0.01). The results during early ischemia (less than 20 minutes of ischemia) are accurately represented by a model of ischemia in which injury current arises only at the ischemic boundary. The results during later ischemia (after 20 minutes of ischemia) may be represented by a model in which ST is considered dependent on injury currents generated throughout the ischemic region.
Depressed responsiveness to vasoconstrictor and dilator agents and baroreflex sensitivity in conscious, newborn lambs.
Authors: Manders W T , Pagani M , Vatner S F
Published: June 2012

The effects of vasoconstrictors and vasodilators were compared in conscious, newborn lambs and adult sheep instrumented with electromagnetic flow probes on the ascending aorta and catheters in the thoracic aorta. Methoxamine, angiotensin II, norepinephrine, nitroglycerin and isoproterenol were administered intravenously to evaluate their effects on arterial pressure, cardiac output and systemic vascular resistance (SVR). The difference in response between adults and newborns was most apparent with methoxamine. Methoxamine, 400 micrograms/kg, i.v., which increased mean arterial pressure by 57 +/- 6% and SVR by 278 +/- 27% in newborn lambs, caused greater increases (p less than 0.01) of 81 +/- 8% and 1418 +/- 141%, respectively, in the adults. Responses also differed significantly between newborn and adult animals to norepinephrine, angiotensin II, nitroglycerin and isoproterenol. In a second group of animals in which smaller amounts of methoxamine and isoproterenol were injected directly into the terminal aorta, changes in terminal aortic flow and resistance were examined. Again, both vasoconstrictor and vasodilator responses were more marked in adults than in newborns. Finally, the sensitivity of the arterial baroreceptor reflex was evaluated by comparing the regression of pulse interval (PI) on systolic arterial pressure (SAP) after an intravenous dose of methoxamine in conscious, adult and newborn animals. The PI/SAP slopes in adult sheep, 45.4 +/- 3.5 msec/mm Hg, were significantly greater (p less than 0.01) than in newborn lambs, 11.7 +/- 2.2 msec/mm Hg.
The electrocardiographic and antiarrhythmic effects of imipramine hydrochloride at therapeutic plasma concentrations.
Authors: Giardina E G , Bigger J T , Glassman A H , Perel J M , Kantor S J
Published: June 2012

The electrocardiographic effects of imipramine hydrochloride at therapeutic plasma concentrations were determined in 44 depressed patients during a 6-week clinical outcome study of depression. During each week of the protocol, i.e., 2 weeks of control and 4 weeks of drug treatment, a standard 12-lead ECG, high-speed, high-fidelity ECG tracings, and a 24-hour continuous ECG recording were obtained. PR, QRS, and QTc intervals, T-wave amplitude, heart rate and frequency of ventricular premature depolarizations (VPDs) were measured. The plasma concentration of imipramine and desmethylimipramine was measured three times a week. Imipramine prolonged the PR (p less than 0.001), QRS (p less than 0.001) and QTc (p less than 0.001) intervals, increased the heart rate (p less than 0.001) and lowered T-wave amplitude (p less than 0.05) during the 4 weeks of treatment. No patient developed high-grade atrioventricular block or severe intraventricular conduction abnormalities. In addition, imipramine had a potent antiarrhythmic action in patients who were recovering from depression. Ten of 11 patients who had more than 10 VPDs/hour had 90% or greater arrhythmia suppression during antidepressant treatment with imipramine at plasma concentrations ranging from 100--302 ng/ml.
Scintigraphic characteristics of experimental myocardial infarct extension.
Authors: Kronenberg M W , Wooten N E , Friesinger G C , Page D L , Higgins S B , Collins J C , O'Connor J L , Price R R , Brill A B
Published: June 2012

Technetium-99m-stannous pyrophosphate scintiphotos were evaluated for diagnosing and quantitating myocardial infarct (MI) extension in sedated dogs. Infarction and extension were produced by serial left anterior descending coronary artery ligations at 0 and 48 hours. We compared serial scintiphoto data with regional myocardial blood flow (MBF) (microsphere technique) and infarct histopathology. In eight control dogs, the scintigraphic MI area was stable at 24, 48, and 72 hours. In each of 11 dogs undergoing extension, the MI area increased after the 48-hour occlusion, averaging a 48.9% increase (p less than 0.001). Grossly, most extensions were mixtures of confluent necrosis and moderate (patchy) necrosis. MBF to confluent infarct tissue decreased significantly, allowing the documentation of extension by totaling the grams of newly flow-deprived tissue, but patchy infarct tissue had little flow deprivation, making it difficult to quantitate this type of extension accurately by flow criteria alone. Rarely, extension could be diagnosed using conventional histologic criteria. We concluded that the scintiphoto MI area was related quantitatively to infarct weight in both control and extension. However, it was not possible to determine that an increase in the MI scintiphoto area was an accurate predictor of the degree of extension using independent flow or pathologic criteria.
Evaluation of transthoracic electrical impedance in the diagnosis of pulmonary edema.
Authors: Fein A , Grossman R F , Jones J G , Goodman P C , Murray J F
Published: June 2012

To evaluate the clinical usefulness of measuring transthoracic electrical impedance in patients with pulmonary edema, we studied 27 normal subjects and 33 patients. In normal subjects, impedance increased when body position changed from supine to standing (p less than 0.01) and when lung volume increased from residual volume to total lung capacity (p less than 0.01). Impedance values vari7 omega) when measured hourly without removing the electrodes. In only five of 11 patients with clinically severe pulmonary edema and five of eight with radiologically severe pulmonary edema were impedance values outside the normal range. Changes in impedance values correlated with changes in clinical and radiographic indexes of pulmonary edema. We conclude that (1) single measurements of impedance are useless in diagnosing pulmonary edema, and (2) impedance changes as predicted as pulmonary edema increases and decreases, and these changes are readily detected by simpler methods of evaluation.
Response of right ventricular ejection fraction to upright bicycle exercise in coronary artery disease.
Authors: Berger H J , Johnstone D E , Sands J M , Gottschalk A , Zaret B L
Published: June 2012

The right ventricular (RV) response to exercise was assessed in 32 patients with angiographically documented coronary artery disease and in 14 normal controls without cardiopulmonary disease. The relationships between exercise RV reserve, exercise left ventricular (LV) reserve, and the presence of proximal right coronary stenosis were also evaluated. RV and LV ejection fractions were determined using first-pass radionuclide angiocardiograms. The normal response to exercise was at least a 5% absolute increase in RV and LV ejection fractions. In the group with coronary artery disease, RV ejection fraction either decreased or remained the same with exercise (abnormal exercise RV reserve) in 19 of 32 patients. LV exercise reserve was abnormal in 26 of 32 patients. All 19 patients with abnormal exercise RV reserve had abnormal exercise LV reserve, and all six patients with normal LV reserve had normal RV reserve. There was a significant linear relationship between the direction and magnitude of change from rest to exercise of LV ejection fraction and RV ejection fraction (r = 0.77). In contrast, the RV response to exercise was not primarily dependent upon the presence or absence of proximal right coronary stenosis. These data suggest that abnormal exercise RV reserve occurs frequently in coronary artery disease and that the concomitant LV response to exercise appears to be its major determinant.
Performance of conventional orthogonal and multiple-dipole electrocardiograms in estimating left ventricular muscle mass.
Authors: Dunn R A , Pipberger H V , Holt J H , Barnard A C , Pipberger H A
Published: June 2012

For estimating left ventricular mass (LVM), ECG criteria for left ventricular hypertrophy (LVH) were selected from conventional 12-lead ECGs, orthogonal three-lead ECGs, and multiple-dipole ECGs (MDECG). The three cardiograms were recorded in 139 patients for whom the degree of LVH was independently determined from biplane ventriculograms. Tested ECG criteria included Sokolow-Lyon measurements for the 12-lead ECG; for the orthogonal ECG, maximal QRS magnitude in the horizontal plane, R duration in the z-lead and Jxyz (spatial magnitude of point J); and for the 126 leads of the MDECG, the dipole activity (DA) of the septum and the free left ventricular wall. Correlation coefficients between LVM and the 12-lead ECG, three-lead ECG and MDECG were 0.61, 0.78 and 0.89, respectively, with corresponding errors of estimated LVM of 103, 82 and 60 g. More complex recording and analytic methods clearly led to increased accuracy in LVM estimates. However, the large error of estimate may limit practical applicability of such correlations. For classification of subjects into normal and above-normal categories, a likelihood ratio was also used and led to a maximum performance index of 86% with MDECG measurements.
Dual atrioventricular nodal pathways: a common electrophysiologic response in children.
Authors: Thapar M K , Gillette P C
Published: June 2012

Electrophysiologic investigation was performed on 61 children and young adults during evaluation of either cardiac dysrhythmia or pre- or postoperative congenital heart disease. The results of these studies were reviewed retrospectively to determine if longitudinal dissociation of the atrioventricular node (AVN) was present. Dual AVN pathways were detected by the atrial extrastimulus technique, using His bundle electrograms. A discontinuous H1H2 response curve indicated the presence of dual AVN pathways. There was a higher incidence of dual AVN pathways in patients with clinically evident paroxysmal supraventricular tachycardia (PSVT) than in those without PSVT. Dual AVN pathways were equally prevalent in children with corrected and uncorrected congenital cardiac defects.
Epicardial mapping of the onset of ventricular tachycardia initiated by programmed stimulation in the canine heart with chronic infarction.
Authors: Klein G J , Ideker R E , Smith W M , Harrison L A , Kasell J , Wallace A G , Gallagher J J
Published: June 2012

The initial beats of ventricular tachycardia (VT) induced by programmed stimulation (PS) of the heart have frequently been observed to differ in QRS configuration from the subsequent uniform QRS complexes of tachycardia. The transient nature of these initial beats has made their study difficult during epicardial mapping with conventional, hand-held recording electrodes. Twenty-four dogs were studied with PS 1-10 months after coronary ligation. Twenty-six epicardial electrograms were recorded simultaneously during PS. The data were digitized for computer generation of isochronic maps for any desired beat. Three patterns of initiation were observed in episodes of tachycardia in which the initial beats differed from the subsequent beats of VT (11 of 18 runs of VT). Most frequently, the initial beats of VT originated near the pacing electrode before moving to a stable infarction zone location. Less frequently, the initial beats were due to transient reentry in the bundle branches or a transient shifting of early breakthrough sites in the infarction zone.
Wolff-Parkinson-White syndrome in children: electrophysiologic and pharmacologic characteristics.
Authors: Gillette P C , Garson A , Kugler J D
Published: June 2012

Intracardiac electrophysiologic studies were performed on 28 infants and children, ages 1 month to 18 years, with the Wolff-Parkinson-White syndrome to try to determine 1) the electrophysiologic characteristics of the accessory connection and 2) the mechanisms of associated supraventricular dysrhythmias. Although the antegrade refractory periods of the normal conduction system were shorter than those found in adults, those of the accessory connection were slightly longer. Reciprocating supraventricular tachycardia (SVT), which had been a clinical problem in 26 of 28, could be induced in the laboratory in all 26 subjects. The mechanism involved reentry with antegrade conduction through the atrioventricular (AV) node and retrograde through the accessory connection in 22. Eleven of these 22 had a wide QRS during tachycardia due to a bundle branch block. Three other subjects had wide QRS tachycardia, but the mechanism involved antegrade conduction through the accessory connection and retrograde through the AV node. The other patient had AV node reentry tachycardia. Two patients did not have clinical SVT, and in these two, SVT could not be induced. Neither patient had retrograde conduction through the accessory connection. The site of the accessory connection could be identified in 26 subjects by the sequence of retrograde activation of the atrium during SVT or ventricular pacing. Digitalis shortened the refractory period of the accessory connection in five of the eight patients studied.
Prospective diagnosis of d-transposition of the great arteries in neonates by subxiphoid, two-dimensional echocardiography.
Authors: Bierman F Z , Williams R G
Published: June 2012

Subxiphoid, two-dimensional echocardiograms (S2DE) were performed and interpreted before diagnostic cardiac catheterization on 59 neonates who weighed 1.3--6.0 kg (median 3.3 kg) and were 1--35 days old (median 4.5 days). The echocardiographic studies were successfully performed on 58 of 59 infants. Using appropriate longitudinal and transverse projections, S2DE permitted simultaneous visualization of the branch pulmonary arteries, proximal thoracic aorta and ventriculoarterial attachments. D-transposition of the great arteries was correctly predicted in all 16 infants with levocardia, situs solitus and atrioventricular concordance. In these patients, the standard left ventricular longitudinal projection demonstrated the bifurcating main pulmonary artery attached to the posterior ventricle; the transverse projection displayed the relationship of the proximal thoracic aorta to the anterior ventricle. The broad acoustical window using the subxiphoid approach in conjunction with a high-frequency focused transducer and a large active-element diameter permitted detailed imaging of intra- and supracardiac structures.
Long-term effects of physical training on coronary patients with impaired ventricular function.
Authors: Lee A P , Ice R , Blessey R , Sanmarco M E
Published: June 2012

Eighteen patients with coronary heart disease and an ejection fraction of 0.40 or less were entered into an individualized exercise training program. Maximal symptom-limited exercise stress test and cardiac catheterization studies were performed initially and 12--42 months (average 18.5 months) after exercise training. At the time of the follow-up study, the mean functional aerobic impairment (FAI) improved from 32.1 to 23.4% (p less than or equal to 0.01); resting and submaximal heart rates were significantly lower (p less than 0.01 and 0.05, respectively). There was no significant change in the pulmonary artery or left ventricular end-diastolic pressure, cardiac index, stroke index, left ventricular end-diastolic volume or ejection fraction. Exercise training, therefore, can be beneficial even for patients with impaired ventricular function. Increase in physical work capacity was not correlated with improvement of ventricular function; on the other hand, exercise training did not cause deterioration of ventricular function.
Mechanical function of the heart and its alteration during myocardial ischemia and infarction. Specific reference to coronary atherosclerosis.
Authors: Swan H J
Published: June 2012

Altered regional mechanical myocardial performance is an early, sensitive marker of myocardial ischemia, and can be estimated in man with reasonable accuracy. Identification, localization and quantification of abnormalities in mechanical performance can be used to predict the presence of coronary artery disease. Testing techniques that have little or no effect on diagnostic efficiency must be replaced with more sensitive indicators of ischemia. If experimental data are validated by findings in human subjects, accurate identification of regional wall motion changes during test conditions should prove to be a powerful marker of ischemia. To be of value, a diagnostic test must strongly increase the frequency of identification of subjects with a high probabilty for the presence of coronary artery disease in an otherwise low-prevalence population, and of those with known disease who are at the highest risk for complications including myocardial infarction or death.
Survival of the ischemic brain: a progress report.
Authors: Scheinberg P
Published: June 2012

The number of patients with cerebral infarctions increases as the population ages, despite campaigns against hypertension, the greatest risk factor. Cerebral ischemia initiates events that are presumed to defer the stage of irreversible injury. These events cause an increase of perfusion around the central ischemic zone and trigger the Bohr effect, both of which preserve tissue viability. Almost simultaneously, mitochondrial function fails, resulting in insufficient energy for the enzyme systems to control Na and K ion equilibrium. At the same time, protein synthesis slows and cellular respiratory enzymes decrease their activity, initiating an irreversible state of tissue change. Tissue fatty acids increase as a result of dissolution of cell membrane lipoprotein structure. Barbiturates reduce the extent of experimental infarction. Resperine and aminophylline are also effective, but there are no corroborative clinical trials. That ischemic brain damage may be the result of toxic substances in the ischemic tissue represents a new concept.
Research related to validation of treatment modalities by large-scale clinical trials.
Authors: Remington R D
Published: June 2012

The history of randomized, controlled, clinical trials is reviewed. Cooperative clinical trials are reviewed and summarized, and specific needs for future trials are identified. Improved policy on resource allocation decisions for clinical trials vs other forms of research is necessary, particularly as such trials begin to translate improved therapeutic knowledge into community level disease control.
Cardiac arrhythmias after chronic embolization of the sinus node artery: alterations in parasympathetic pacemaker control.
Authors: Loeb J M , Euler D E , Randall W C , Moran J F , Brynjolfsson G
Published: June 2012

Embolization of the sinus node artery was accomplished in dogs by injecting rapidly hardening vinyl latex into the sinus node artery. Embolization immediately shifted the pacemaker to a junctional focus; however, with time postoperatively, the pacemaker shifted to an atrial site. Variable episodes of pacemaker failure, sinoatrial block, junctional rhythm, wandering atrial pacemaker and idioventricular escape rhythms were commonly observed on Holter monitor in isolation but only rarely when the dog was in the laboratory. Severe bradycardia (38.9 +/- 3.7 beats/min) was the predominant rhythm by 3-6 months postoperatively. In addition, these same dogs had a greater overall increase in heart rate after atropine than normal dogs (17.5 +/- 13.5 vs 116.6 +/- 15.9 beats/min above control; p less than 0.02). Responses to vagal stimulation in this group were abnormal, as long periods of asystole and bradycardia were observed after stimulation was terminated. These data suggest an alteration in parasympathetic pacemaker control after chronic embolization of the sinus node artery.
Evaluation of transluminal angioplasty of chronic coronary artery stenosis. Value and limitations assessed in fresh human cadaver hearts.
Authors: Lee G , Ikeda R M , Joye J A , Bogren H G , DeMaria A N , Mason D T
Published: June 2012

The possibility of increasing reduced blood flow in atherosclerotic coronary obstruction by catheter balloon dilatation offers a nonsurgical approach to relieve clinical coronary stenosis. To assess the ability of effectively dilating such diseased vessels by transluminal angioplasty, we used the Grüntzig balloon-tipped catheter in 12 fresh human cadaver hearts in which the intervention was performed in 21 noncalcified stenotic areas, including each of the three major coronary arteries. Quantitative coronary arteriography documented decreased obstruction of each lesion; luminal diameter increased 58% (1.9 +/- 0.2 mm to 2.8 +/- 0.3; p less than 0.001) and luminal diameter relative to the most proximal normal coronary segment diminished 61% (46 +/- 4% to 18 +/- 3%; p less than 0.001). Angioplasty was most successfully applied in proximal, discrete, noncalcified lesions of the right and left anterior descending coronaries; calcified, tortuous, middle and distal lesions and the left circumflex coronary were entered with difficulty or unapproachable. Histologic examination revealed microanatomic changes, most often endothelial disruption and atheroma compression, but no serious vascular tears. Dilatation beyond normal coronary diameter caused vessel rupture. This study extends elucidation of the value and limitations of percutaneous transluminal angioplasty in the clinical use of this technique in selected patients for relieving coronary obstruction without surgery.
Selective coronary arteriography in children.
Authors: Formanek A , Nath P H , Zollikofer C , Moller J H
Published: June 2012

Anomalies and disease processes of the coronary arteries in children are uncommon. However, with the recent advances in cardiac surgical techniques, many of these lesions are amenable to surgery that requires accurate anatomic delineation by angiography. Ascending aortography is the angiographic procedure commonly used to image the coronary arterial anatomy in children. In some instances this procedure fails to show the extent or nature of the pathologic process. In some cases, selective coronary arteriography is essential for successful management. Twelve patients are presented in whom selective coronary arteriography was indicated, and its value is compared with that of nonselective angiography. Indications for selective coronary arteriography in children are given, and its complications are also discussed.
Renal effects of nitroprusside and hydralazine in patients with congestive heart failure.
Authors: Cogan J J , Humphreys M H , Carlson C J , Rapaport E
Published: June 2012

The acute effects of nitroprusside infusion and intravenous hydralazine on renal hemodynamics and function were evaluated in nine male patients with severe, low cardiac output, congestive heart failure (CHF). Both drugs resulted in marked systemic hemodynamic improvement. Nitroprusside had a more profound effect on pulmonary artery pressure, while hydralazine produced a greater elevation in cardiac output. Significant decreases in both systemic and pulmonary vascular resistance and pulmonary capillary wedge pressure with increases in stroke volume and stroke work index were noted with both drugs. Total renal resistance decreased and renal blood flow (RBF) significantly increased with both drugs, while the distribution of cardiac output to the kidney remained depressed. Glomerular filtration rate (GFR) did not change significantly with either drug, although increases in GFR were seen in selected patients in whom RBF increased by more than 10% from control. The fraction of plasma filtered decreased toward normal with both drugs and excretion of total cations was significantly increased. These changes all represent improvements in systemic and renal hemodynamic abnormalities occurring in patients with CHF; their maintenance during long-term therapy would facilitate patient management.
Right ventricular volume determinations in 18 patients with pulmonary atresia and intact ventricular septum. Analysis of factors influencing right ventricular growth.
Authors: Patel R G , Freedom R M , Moes C A , Bloom K R , Olley P M , Williams W G , Trusler G A , Rowe R D
Published: June 2012

Right ventricular growth was assessed angiocardiographically in 18 patients with pulmonary atresia, intact ventricular septum, and hypoplastic and hypertensive right ventricle. A variety of surgical procedures were performed. In only 12 patients (66.7%) was right ventricular-pulmonary artery continuity achieved (group 1). Nine of these 12 patients persisted with systemic or suprasystemic right ventricular pressures. Among the six patients in whom right ventricular-pulmonary artery continuity was not achieved (group 2), all maintained suprasystemic right ventricular pressures. Right ventricular growth was assessed in groups 1 and 2. The patients were also subdivided according to the qualitative degree of tricuspid regurgitation as determined angiocardiographically on right ventricular cineangiocardiograms at the preoperative catheter study. Right ventricular growth to normal levels as evidenced by change in right ventricular end-diastolic volume was rarely observed in group 2 patients. Among the four patients with severe tricuspid regurgitation and a large tricuspid valve, right ventricular growth to normal levels was achieved whether they were in group 1 or group 2. Right ventricular growth is thus predicated on numerous morphologic factors in these patients. However, reconstitution of right ventricular-pulmonary artery continuity and a nonobstructive tricuspid valve are probably two of the more important factors.
Radionuclide and hemodynamic assessment of left ventricular functional reserve in patients with left ventricular aneurysm and congestive cardiac failure. Response to exercise stress and isosorbide dinitrate.
Authors: Stephens J D , Dymond D S , Spurrell R A
Published: June 2012

The hemodynamic response to exercise stress was assessed in 17 patients with left ventricular (LV) aneurysm, demonstrated by contrast left ventriculography, and congestive cardiac failure (CCF) before and after sublingual isosorbide dinitrate (ISDN). Radionuclide ventriculography was performed at rest and during exercise in 14 patients. ISDN increased mean exercise LV stroke work index (LVSWI) from 31 to 39 g-m/m2 (p less than 0.001) and reduced mean exercise LV filling pressure from 38 to 25 mm Hg (p less than 0.001). Using the combined criteria of LVSWI and ejection fraction of the contractile section of the left ventricle (EFCS), no patient with rest EFCS of less than 40% achieved a good absolute response to exercise in LV performance with or without ISDN. Of the six patients with rest EFCS greater than or equal to 40% only three achieved a good response. While rest EFCS less than 40% indicates poor LV functional reserve, good LV functional reserve is not always indicated by rest EFCS greater than or equal to 40%.