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Biomedical subjects

N de Soyza

Publications and source records attributed to N de Soyza.

15 recordsLinked to original sources
PubMed1979

The reliability of coronary angiogram interpretation: an angiographic-pathologic correlation with a comparison of radiographic views.

This prospective study correlates premortem coronary angiographic interpretation with pathologic findings including the use of postmortem coronary angiograms. The reliability of a single radiographic view, left anterior oblique or right anterior oblique, or combined views (left anterior oblique plus right anterior oblique) was examined. The most reliable interpretation, the combined view, has a specificity of 93 per cent, but sensitivity is less at 61 per cent. Using a single view enhances diagnosis (sensitivity), but it leads to overestimation more frequently (decreased specificity). Proximal segments of the coronary arteries are prone to a significant per cent of false positive readings. The most accurate assessment of the anterior descending coronary artery system occurs with the use of the right anterior oblique with multiple views. Less routine use of the left anterior oblique view with increased use of the hemiaxial view is suggested for the angiography of the left coronary artery. Initial cusp injections of the right coronary artery may avoid a high per cent of false positive readings in the proximal segment.

Angiography↗
PubMed1979

Evaluation of warning arrhythmias before paroxysmal ventricular tachycardia during acute myocardial infarction in man.

In order to determine the relationship of paroxysmal ventricular tachycardia (PVT) to any antecedent (premonitory) ventricular arrhythmias during the early phases of acute myocardial infarctions, 24-hour Holter monitoring was begun on 52 male patients an average of 12.6 hours after the onset of prolonged chest pain that was documented as acute infraction. Twenty-four patients had PVT and 28 did not. We analyzed in detail the incidence of frequency of premature ventricular complexes (PVCs), prematurity and pairing during the 10 minutes immediately preceding PVT from a continuous 10-minute rhythm strip. There was no positive correlation between PVT and the number or complexity of PVCs in the 10 minutes immediately before ventricular tachycardia. These findings suggest that there is no consistent pattern or frequency of ventricular arrhythmia that could be identified as premonitory for PVT during the immediate pre-PVT period, even during the acute phase of myocardial infarction in man.

Acute Disease↗
PubMed1978

Coronary angiogram interpretation. Interobserver variability.

Clinicopathological correlation of premortem coronary angiograms and postmortem data was performed to determine the degree of interobserver variability in the clinical interpretation of coronary angiograms using the pathological findings as the standard of accuracy. Comparison of the independent interpretations of the antemortem coronary angiograms by three cardiologists showed no substantial difference in overall diagnostic accuracy among the three observers. In the majority of instances where a substantial angiographic lesion was found on coronary angiography, it was verified pathologically. In false-positive or false-negative interpretations, a majority opinion was accurate when compared with a pathological lesion in 50% of the instances. Despite the fact that coronary angiography is an excellent diagnostic tool, there remain limitations of the accuracy of interpretation not solved by a majority opinion.

Angiography↗
PubMed1978

The relationship of paroxysmal ventricular tachycardia complicating the acute phase and ventricular arrhythmia during the late hospital phase of myocardial infarction to long-term survival.

The long-term prognosis of paroxysmal ventricular tachycardia (PVT) complicating acute myocardial infarction remains unevaluated. Significant ventricular arrhythmia in the patient after infarction is said to carry a poor prognosis with regard to survival. To evaluate these two important aspects of myocardial infarction in man, 56 patients with documented myocardial infarction had Holter monitoring performed during the initial 24 hours and prior to hospital discharge. In 38 of the 45 survivors, Holter monitoring was repeated an average of 19 months after infarction. There were eight cardiac deaths during follow-up. Data analysis revealed that of 18 patients with PVT during the acute phase, one died during follow-up and 17 survived long-term. Even though the incidence of complex PVCs prior to hospital discharge and at long-term follow-up was higher in patients with PVT during the acute phase than in those without PVT, survival appeared unaffected. Thus, PVT during the acute phase of myocardial infarction and complex PVCs at the time of hospital discharge are not incompatible with long-term survival.

Acute Disease↗
PubMed1978

Ventricular arrhythmias in chronic stable angina pectoris with surgical or medical treatment.

Since both propranolol therapy and saphenous-vein bypass surgery have become accepted treatments for patients with symptomatic coronary-artery disease, it is important to determine if either influences the prevalence of ventricular arrhythmias in these patients. Six-hour dynamic electrocardiography was done on 130 patients with chronic stable angina pectoris at least 1 year after being randomized to surgical or medical therapy. All surgical patients had saphenous-vein grafting; 90% of the medical patients received propranolol. Data analysis showed that even though the overall prevalence of premature ventricular contractions was no different in medical and surgical patients, the prevalence of complex premature ventricular contractions was significantly higher in surgically treated patients not receiving propranolol than in propranolol-treated medical patients (p less than 0.05). However, the survival rate was no different in either group, and the quality of life in the surgical patients remained superior.

Adult↗
PubMed1977

Dual effects of concealed A-V nodal conduction in man.

An interpolated premature ventricular contraction (PVC) may produce either complete block of the next sinus impulse or depression of A-V nodal conduction with a prolonged A-H interval. When a PVC results in partial depression of a A-V nodal conduction, the effect on subsequent premature atrial stimuli is unknown. The authors have recently observed three patients in which the effect of a premature ventricular stimulus with interpolation on the functional refractory period of the A-V node could be measured. In case one an interpolated PVC sufficient to prolong the A-H interval from 80 to 120 msec was followed by programmed premature atrial stimuli which resulted in no additional A-V nodal delay, and the apparent functional refractory period of the A-V node was reduced from 420 to 330 msec when compared with the atrial extrastimulus technique. In case two a programmed ventricular extrastimulus prolonged the A-H interval in the following sinus beat from 120 to 240 msec; atrial extrastimuli then resulted in only minimal increments in A-V nodal delay and the apparent functional refractory period of the A-V node was reduced from 590 msec. A ventricular extrastimulus in case three increased the resting A-H interval from 60 to 115 msec; conduction of atrial extrastimuli then resulted in a reduction in the functional refractory period of the A-V node from 465 to 400 msec. In each case an interpolated premature ventricular stimulus produced (1) depression of A-V nodal conduction in the ensuing sinus beat A1 and (2) relative facilitation of A-V nodal conduction of a subsequent premature atrial stimulus (A2). The functional refractory period of the A-V node was reduced when compared with the atrial extrastimulus technique alone.

Atrioventricular Node↗
PubMed1977

Experimental production of manifest and concealed ventricular rhythms in man.

Analysis of clinical ventricular ectopy has provided deductive evidence for the existence of concealed ventricular rhythms. Studies in the experimental animal have demonstrated that when ventricular extrastimuli are applied near the ventricular effective refractory period of consecutive sinus beats, extrastimuli may not be conducted after sinus beats immediately following the post-estrasystolic pause. This sequence may be due to a prolongation of the effective refractory period of ventricular muscle produced by the increased cycle length resulting from the post-extrasystolic pause. The purpose of this study was to extend these observations to the human ventricle in an attempt to produce concealed ventricular rhythms by programmed ventricular extrastimuli. Twelve patients with normal PR intervals and QRS complexes with a mean age of 49 years were studied with ventricular extra-stimuli at programmed intervals following normally conducted sinus impulses. Premature ventricular impulses were introduced after every sinus beat at intervals 10 to 120 msec outside the effective refractory period. In eleven patients without ventricular interpolation, stimuli applied within 40 msec of the effective refractory period produced from one to three concealed (non-conducted) ventricular stimuli following the post-extrasystolic pause; stimuli applied greater than 40 msec outside the effective refractory period at identical current levels produced manifested bigeminy in all cases. In one patient with interpolated premature ventricular beats without a compensatory pause, programmed ventricular extrastimuli produced manifest bigeminy at all coupling intervals. This study demonstrates the experimental production of concealed and manifest ventricular rhythms in man and confirms the importance of the relationship between the ventricular effective refractory period, the timing of the premature ventricular impulse, and the occurence of a compensatory pause.

Electric Stimulation↗
PubMed1977

Pharmacokinetics of digoxin.

The pharmacokinetics of digoxin, the most frequently used digitalis preparation, are reviewed. The dominate serum turnover time is about 34 hours, and is not affected by the route of administration. Excretion is largely as unchanged digoxin in the urine and this excretion is compromised in renal failure. Serum levels of digoxin (determined by radioimmunoassay) are generally available and are useful clinically in assessment of both toxicity and the state of underdigitalization, even though significant overlap exists. Special problems are presented in patients with myocardial infarction, pulmonary heart disease, and thyroid disease.

Acute Kidney Injury↗
PubMed1976

The relation of sinus rate to the frequency of paroxysmal ventricular tachycardia during acute myocardial infarction in man.

Continuous tape recordings of cardiac rhythm were made in 51 male patients with acute myocardial infarction within 24 hours of their infarction. These tracings were analyzed for the incidence of paroxysmal ventricular tachycardia (PVT) and the sinus rate immediately preceding each episode of PVT. In 26 patients, 112 episodes of PVT at a rate greater than 100 beats/min were documented. Although 67 per cent of the episodes of PVT were preceded by sinus rates between 60 and 100 beats/min, 15 per cent occurred at sinus rates below 60 beats/min and 18 per cent occurred at sinus rates above 100 beats/min. The data remained essentially unchanged regardless of whether ventricular tachycardia was defined at rates in excess of 100, 120 or 140 beats/min. The results of this study show that during the early phases of acute myocardial infarction in man, PVT was most common during sinus rates generally thought to be within the normal range (60 to 100 beats/min). A lower, but close to equal incidence of PVT was observed during sinus bradycardia and sinus tachycardia.

Adult↗
PubMed1976

Comparison of the effects of atrial and ventricular stimulation on sinus node function in man.

Although sinus node function has been evaluated during premature atrial stimulation, no study of retrograde ventriculoatrial sinus node activation following premature ventricular stimuli has been reported. The purpose of this study was to investigate the production of compensatory and noncompensatory pauses by premature ventricular contractions through a comparison of the effects of atrial and ventricular stimulation on sinus node function. Eleven patients in sinus rhythm were studied with programmed introduction of premature atrial and ventricular stimuli outside the ventricular vulnerable period. The onset of sinus node reset, duration of return sinus cycle (A2-A3) during reset, and estimated sinoatrial conduction times were recorded. Sinus node function during premature ventricular stimulation was approximated by utilizing the interval between the last sinus beat and onset of retrograde atrial depolarization (A1-A2 interval). The return cycle length (A2-A3) during sinus reset compared at equal A1-A2 intervals was significantly less with ventriculoatrial conduction (1,145 +/- 52 msec. atrial vs. 1,076 +/- 52 msec ventriculoatrial; P less than 0.01 by paired t test) and the estimated sinoatrial conduction time was significantly less with ventriculoatrial conduction (71 +/- 7 msec. atrial vs. 25 +/- 7 msec. ventriculoatrial; P less than 0.01 by paired t test). Ventriculoatrial sinus reset occurred later in the sinus cycle than atrial reset in three of seven patients with sinus reset produced by both atrial and ventricular prematures. This study shows that the effects of ventriculoatrial conduction on sinus node function are significantly different from those of atrial stimulation alone. The return sinus cycle length during reset and estimated sinoatrial conduction time are significantly reduced with ventriculoatrial conduction. Although the zones of sinus reset with atrial and ventricular stimulation are approximately equal, ventriculoatrial depolarization may produce sinus reset later in the sinus cycle in some cases.

Adult↗
PubMed1976

Improved sinus node sensing after atropine.

Although atropine is known to increase sinus rate through its vagolytic effect, the effects of atropine on sinus node sensing are unknown. The purpose of this study was to investigate alterations in sinus node sensing produced by atropine. Measurement of the zone of sinus node reset and sinoatrial conduction time was performed in 10 patients by programmed premature atrial stimulation. The zone of sinus node reset was determined as the transition point where premature atrial stimuli were followed by a less than compensatory pause. Sinoatrial conduction time was calculated from sinus node return cycles in the area where sinus node reset occurred. Atropine administration produced a significant increase in the percentage of the sinus cycle length at which premature atrial contractions penetrated and reset the sinus node. Sinus node reset occurred at a mean percentage of the sinus cycle of 71 +/- 8 per cent before atropine and 83 +/- 5 per cent after atropine (P less 0.01). The sinoatrial conduction time was significantly reduced from 109 +/- 29 to 62 +/- 23 msec. (P less than 0.01) from atropine as sinus cycle length was reduced from 909 +/- 118 to 642 +/- 75 msec. after atropine. Sinus node echoes were observed in two patients. In one patient atropine abolished the appearance of sinus node echoes. In the second patient atropine reduced the coupling interval necessary to produce sinus node echoes but appeared to facilitate sinus node re-entry by the appearance of an additional sinus node echo and a reduction in the echo cycle length. This study demonstrates that atropine produces significant improvement of sinus node sensing in man.

Angina Pectoris↗
PubMed1975

Altered refractory periods in patients with short P-R intervals and normal QRS complex.

To evaluate the refractory periods of the atrioventricular (A-V) conducting system in patients with a short P-R interval and normal QRS complex, 57 patients with a P-R interval of 110 to 280 msec were studied with His bundle recording and premature atrial stimulation at similar cycle lengths of 660 to 720 msec. In 13 patients with a short P-R interval (120 msec or less) the mean value for the functional refractory period of the A-V node was 368 plus or minus 36 msec (standard deviation), which was significantly lower (P smaller than 0.01) than the mean value of 415 plus or minus 50 msec in 36 patients with a normal P-R interval (between 120 and 200 msec) and the mean value of 492 plus or minus 57 msec in 8 patients with an increased P-R interval (200 msec or greater). Patients with a short P-R interval had a mean value for the effective refractory period of the A-V conducting system of 247 plus or minus 26 msec, which was significantly lower (P smaller than 0.01) than the mean values of 297 plus or minus 51 msec in patients with a normal P-R interval and 369 plus or minus 87 msec in patients with an increased P-R interval. The results identify a characteristic conduction abnormality that is compatible with a partial A-V nodal bypass or dual A-V nodal conduction pathways. The relation between the duration of the P-R interval and the regractory period may aid understanding of the clinical significance of the scalar electrocardiogram.

Adult↗
PubMed1975

In-hospital mortality after acute myocardial infarction.

In order to determine if the risk factors contributing to mortality from acute myocardial infarction (MI) during the period of coronary care unit (CCU) observation are different from those in patients dying in the hospital after CCU discharge, the hospital records of 172 acute MI patients seen over an 18-month period were reviewed. Of the 32 deaths from acute MI, 25 per cent occurred suddenly outside the CCU. The risk factors identified in the 32 deaths were (1) anterior MI (2) Previous MI, (3) cardiac failure, (4) significant ventricular arrhythmia, (5) intraventricular conduction defects, and (6) murmur suggestive of papillary muscle dysfunction. These same risk factors were found to be far more frequent in the patients dying suddenly outside the CCU.

Adult↗
PubMed1975

Tritiated digoxin: studies in renal disease in human subjects.

Digoxin is excreted primarily in the urine as the unchanged glycoside: 60-80% can be recovered from the urine in 7 days after a single intravenous dose in the human subject. Definition of the role of the kidney in digoxin excretion, turnover and metabolism was studied in 57 patients with renal disease, transplant candidates and/or donors and recipients of renal transplants. A single dose of 3H digoxin was given to the subjects, frequent serum samples were obtained and all urine and stools were saved for 7 days. All specimens were extracted with chloroform and digoxin, and its metabolites were separated by column chromatography. Results reveal that the serum T1/2 and the dominant T1/2 of digoxin are prolonged in renal disease in direct proportion to the reduction in creatinine clearance (r = 0.833). The blood urea nitrogen (BUN) is also related to digoxin clearance (r = 0.742). The higher the BUN, the less digoxin excreted in the urine. Anephric patients excrete more digoxin in stool, but this does not compensate for the lack of renal excretion. Transplanted kidneys excrete digoxin in proportion to renal functional capacity, as do patients who have experienced unilateral nephrectomy. Peritoneal or hemodialysis is not effective in removing digoxin from the human subject and may lead to digitalis intoxication if K+ is allowed to fall to critical levels. Digoxin excretion is not volume related, as patients with nephritogenic diabetes insipidus excrete the drug normally with urine volumes of 12 liters a day. Digoxin doses in renal insufficiency should be dictated by knowledge of renal functional ability of the kidneys and after "normal" loading doses, and maintenance doses should be 1/4 to 1/2 those usually administered.

Adult↗