Pseudo-on-line fast response microvessel dimensions video graphic recorder with electrical signal output

The present article describes a new method of microvessel dimensions measurement in which a writing oscilloscope is used to continuously and graphically record the microvessel video signal from television microscopy at a fast rate of 50 records per second. Dimensions of interest, such as the microvessel red blood cell flux diameter, are then easily marked out manually from the graphic records and a dynamic electrical signal proportional to the dimensions is generated. The signal is then recorded on one channel of a multichannel voltage recorder and is synchronised with other experimental signals which have previously been recorded on-line during the experiment. The result is that the dimension signal appears to have been recorded on-line during the experiment as well. This is desirable for electronic signal correlation and processing. This method is useful when poor experimental conditions, commonly encountered, make automatic recording of microvessel dimension unsatisfactory and manual inspection and processing become necessary.

Tibial lengthening apparatus with distractive force measurement system

A tibial lengthening apparatus has been developed which incorporates a distractive force measurement system. Lengthening is carried out generally in accordance with the 2-stage Anderson method. After closed percutaneous osteoclosis (clinically performed fracture), the tibial fragments are held in place by Steinmann pins and novel Steinmann pin-clamping blocks to ensure rigid fixation and accurate alignment. The blocks provide electrical insulation between the patient and the apparatus and are able to accommodate different sizes of Steinmann pins and misalignment of the pins as a result of their insertion in the tibia by drilling. A metric distraction mechanism provides controlled lengthening and the distractive force is sensed by two transducers, each consisting of an aluminium ring to which are bonded electrical resistance strain gauges in a full bridge configuration. Electronic instrumentation is used to process the transducer signals and the resulting force readings are displayed on a digital panel meter as well as being recorded on a digital printer.

Congenital pulmonary artery branch stenosis: association with renal artery stenosis

A patient had multiple bilateral stenoses of the pulmonary artery and its branches with systemic hypertension associated with mild stenoses of the renal arteries. Cardiac catheterization and angiocardiography are important in the evaluation of the degree of stenoses and pulmonary hypertension. This case suggests that in a child or young person with hypertension and a loud precordial murmur, lesions other than coarctation of the aorta may be present. Unexplained systemic hypertension requires further investigative workup which is essential for proper treatment and long-term management of these patients.

Effects of phenytoin on refractoriness and conduction in the human heart

Using His bundle electrograms and the atrial (A2) and ventricular extrastimulus (V2) techniques, anterograde and retrograde refractory period studies were performed (in 9 and 12 patients, respectively) before and 10 min after intravenous infusion of phenytoin (DPH; mean plasma level, 17.3 micrograms/ml). DPH had no effect on the duration of the QRS complex or the H-V interval of the sinus beats; it had variable but insignificant effects on the sinus rates and the atrial, A-V nodal, and ventricular muscle refractoriness. With the use of the A2 technique, the effective refractory period (ERP) of the His-Purkinje system (HPS) could not be determined in any patient; the relative refractory period (RRP) of the HPS could be determined in 2/9 patients and shortened in both patients after DPH. With the use of the V2 technique, retrograde functional refractory period (FRP) and RRP of the HPS could be determined in all 12 patients and the retrograde ERP of the HPS in 7/12; DPH significantly shortened all these parameters (p less than 0.001, less than 0.001, and less than 0.005, respectively). Functional refractory period of the ventriculo-atrial conduction system (VACS) could be determined in 11/12 patients during control studies (the remaining one patient had complete ventriculo-atrial block). DPH significantly shortened the FRP of the VACS in those (4) patients (Group I) in whom it was determined primarily by the HPS (p less than 0.025), and had variable but insignificant effects on FRP of the VACS in the other seven patients (Group II) in whom it was determined almost exclusively by the A-V node. DPH significantly decreased the retrograde HPS conduction times of the premature impulses (V2H2 intervals) for the same coupling (V1V2) intervals (p less than 0.001). It is concluded that, in the human heart, DPH exerts its most important effects on the HPS where it significantly decreases refractoriness and enhances conduction of the premature impulses. This study also demonstrates that the V2 technique is far superior to the A2 technique for evaluating the effects of drugs on refractoriness and conduction in the HPS.

Multiple mechanisms of tachycardias in a patient with the Wolff-Parkinson-White syndrome

In a patient with the Wolff-Parkinson-White Syndrome we observed atrial fibrillation and three distinct paroxysmal re-entrant tachycardias. Intracardiac electrograms obtained during the tachycardias showed the mechanisms to be A-V nodal, accessory pathway and sinus node re-entry. When P wave morphology, R-P relationship and QRS configuration are considered, it is illustrated how these four tachyarrhythmias may be successfully diagnosed on the surface electrocardiogram. The therapeutic implications of multiple arrhythmias with different mechanisms in the Wolff-Parkinson-White Syndrome are discussed.

The effect of digitalis on refractoriness of the intact canine His-Purkinje system

The effect of therapeutic doses of digitalis on functional (F), relative (R) and effective (E) refractory periods (RP) of the His-Purkinje system (HPS) was studied in 12 open-chested, innervated adult mongrel dogs (10-20 kg) during control and 15, 30 and 45-60 min after 0.016 mg/kg of intravenous ouabain. To determine the stability of the preparation and to assess time-dependent changes in His-Purkinje refractoriness, another six dogs (Group II) had similar studies, but without drug administration. In all dogs, the His bundle was paced by using the plunge wire technique at a predetermined cycle length (CL) and a premature stimulus (S2) to the His bundle was introduced at decreasing S1 S2 intervals. Following ouabain, in Group I dogs, at the longest Cls tested (458 +/- 125 msec; +/- SD) there was significant increase in the FRP (+4.34%; P less than 0.05), RRP (S2 V2 (+6.57%, P less than 0.05), RRP (Ab) (+6%, P less than 0.05) and ERP (52%, P less than 0.05) of the HPS. These significant changes were generally observed 30 minutes after drug administration. Changes in RPs were of greater magnitude at longer CLs (greater than 400 msec), but insignificant at shorter CLs (less than 400 msec). The H-V interval during sinus rhythm and the S1 V1 interval during His bundle pacing at all CLs did not change after ouabain. In Group II dogs there were no significant change in His-Purkinje refractoriness over 60 minutes. These findings suggest that therapeutic doses of digitalis 1) tend to increase refractoriness within the HPS to a very small degree, 2) have no appreciable effect on His-Purkinje conduction, and 3) affect CL-dependent changes in refractoriness. The His bundle extrastimulus method is useful in studying the HPS in the intact heart.

Modification and abolition of re-entry within the His-Purkinje system in man by diphenylhydantoin

The phenomenon of macrore-entry (Re) within the His-Purkinje system (HPS) was consistently observed in 10 of 19 patients during retrograde refractory period studies. Effects of intravenous infusion of diphenylhydantoin (DPH) on Re were studied in these 10 patients 10 minutes after completion of infusion (mean plasma level equal to 17.0 microgram/ml). Diphenylhydantoin modified determinants of Re in seven patients (group I) and abolished Re in the remaining three patients (group II). In group I, DPH shortened the critical V1 V2 from 310.0 +/- 30.5 to 292.9 +/- 25.6 msec (P less than 0.025) and critical V2 H2 intervals for Re from 201.4 +/- 18.4 to 185.0 +/- 13.8 msec (P greater than 0.05). In group II, DPH abolished Re in two of three patients by precluding attainment of critical V2 H2 intervals whereas Re was abolished in the remaining one patient despite attainment of critical V2 H2 intervals (vs control). For both groups, DPH significantly shortened functional and effective refractory periods of the HPS (P less than 0.001 and less than 0.01, respectively) without significantly affecting the effective refractory period of the ventricular muscle. Diphenylhydantoin either completely abolished or significantly shortened the retrograde gap zones in the HPS. It is concluded that diphenylhydantoin significantly shortens His-Purkinje system refractoriness, abolishing Re in the patients with higher degree of improvement in refractoriness.

P loops during common and uncommon atrial flutter in man

Atrial flutter has never been satisfactorily defined. The 'common' pattern of flutter was originally described by Lewis in 1913. Less frequently observed forms of flutter are termed 'uncommon'. Sixteen cases of the 'common' and 6 of the 'uncommon' type have been studied using isolated P loop vectorcardiography. All patients had some degree of atrioventricular block but none had evidence of digitalis excess. The atrial rates were regular and were in a range between 250 and 330/minute. Vagal manoeuvres increased AV block in each instance. All those with the 'common' type of flutter had P loops with a caudad-cephalad orientation and fifteen of the sixteen had forces which descended over the right atrium and ascended over the left atrium. The 6 cases of the uncommon type of flutter had rates which ranged between 250 and 300/minute and did not fulfil both of the criteria for 'common' flutter; namely continuous baselineu ndulation and prominent negative P deflections in the inferior leads. The cases with the 'uncommon' type of flutter had a variety of loop patterns. The most frequent type was oriented inferior slightly to the right and anterior. One patient satisfied criteria for left atrial flutter. In another the loop was oriented inferior leftward and anterior. The vectorcardiogram provides a rich source of descriptive data but does not identify the underlying mechanism(s) of flutter.

The 1,2,3,4 phenomenon. Atrioventricular nodal gap in the dog

This study confirms the facility with which the so-called 1,2,3,4 phenomenon can be reproduced in intact dog hearts. When a series of three atrial premature beats (A2, A3, A4) were delivered following a constant A1-A1 drive, we demonstrated a narrow zone of A1-A3 and A1-A4 intervals in which A4 conducted to the ventricles in the presence of A3 but not in its absence. We used His bundle and multiple atrial electrograms to produce the phenomenon in nine of 16 dogs. Facilitation of conduction of A4 (1) occurred above the His bundle, (2) occurred within narrow ranges of A1-A3 and A1-A4 intervals, (3) required penetration of A3 into the atrioventricular (AV) node, (4) required critically long A2-H2 intervals, (5) always was associated with prolonged A4-H4 intervals, and (6) was limited by atrial refractoriness. An apparent or pseudo-1,2,3,4 phenomenon demostrated in five of 16 dogs occurred with (1) latency between S4 and A4, (2) a sinus nodal or atrial reentry beat, or (3) an atrial escape beat. In the absence of A3, A4 could be made to conduct by preexciting the ventricle in advance of V2. We found no evidence for dual AV nodal pathways. Our results suggest that the underlying mechanism for the 1,2,3,4 phenomenon is analogous to the phenomenon of the gap in AV conduction.

Abnormal Q waves in Wolff-Parkinson-White syndrome. Incidence and clinical significance

Between January 1970 and January 1975 the diagnosis of Wolff-Parkinson-White syndrome was entertained in 44 patients. Thirty-one (70%) of these patients had negative sigma-deflections (Q waves) on one or more electrocardiographic leads, thereby simulating a pattern of myocardial infarction (Mi). Fifteen patients (34%) were initially referred with an erroneous diagnosis of Mi based on the presence of Q waves. In nine of these 15 patients, the referring diagnosis was Mi plus ventricular preexcitation; in six, the diagnosis of ventricular preexcitation was overlooked entirely. The incidence of misdiagnosis (34%) was exactly the same as that reportly by Wolff and White approximately 30 years ago. Erroneous diagnosis of Mi can be virtually eliminated by normalizing the QRS complex by premature stimulation of the atrium during the effective refractory period of the accessory pathway.

Interventricular septal motion during preexcitation and normal conduction in Wolff-Parkinson-White syndrome: echocardiographic and electrophysiologic correlation

Interventricular septal motion was studied by echocardiogram in 20 consecutive patients with documented Wolff-Parkinson-White (WPW) syndrome before and during electrophysiologic evaluation using His bundle recordings and pacing techniques. Characteristic abnormal interventricular septal motion was seen in 8 of 11 patients with type B WPW syndrome (groups I and II). All eight patients had electrocardiographic patterns consistent with an anomalous pathway located in the anterior right ventricular wall (group I). In five of these eight patients normalization of the QRS complex for one or more beats was accomplished and produced normalization of the septal motion in four; whereas in the fifth patient, who had an underlying atrial septal defect, the abnormal septal motion remained abnormal. All nine patients with type A WPW syndrome (groups III to V) had normal septal motion both during total preexcitation and during normalization of the QRS complex. The normalization of the abnormal interventricular septal motion with normalization of the QRS complex in type B WPW syndrome strongly suggests that the abnormal motion is related to an abnormal sequence of ventricular depolarization during preexcitation. Furthermore, persistent abnormal septal motion after normalization of the QRS complex suggests that other factors such as right ventricular volume overload may be responsible. Likewise, when abnormal septal motion occurs in the presence of type A WPW syndrome, an explanation other than preexcitation must be sought.

Electrophysiologic effects of procainamide in subtherapeutic to therapeutic doses on human atrioventricular conduction system

The effects of single intravenous infusions of 50 to 400 mg of procainamide on the functional properties of the atrioventricular (A-V) conduction system were studied in 36 patients and correlated with plasma concentrations. A 50 mg dose of procainamide resulted in a plasma concentration of less than 1.0 mug/ml and produced no electrophysiologic changes. Doses of 100, 200, 300 and 400 mg resulted in progresively increasing plasma concentrations (1.2, 1.8, 3.5 and 4.2 mug/ml, respectively). The effects of procainamide on the sinus rate were variable and not dose-related. The effects of doses of up to 300 mg on A-V nodal conduction were variable and not dose-related. Only in a dose of 400 mg did procainamide prolong A-V nodal conduction in six of seven patients. Whereas 100 mg had no effect on His-Purkinje system conduction, doses of 200, 300 and 400 mg prolonged His-Purkinje system conduction time by 6, 8 and 9 msec, respectively. Dose-related increases in atrial refractoriness started with a dose of 200 mg and became statistically significant with doses of 300 and 400 mg. The effects of procainamide on A-V nodal functional refractoriness were variable and not dose-related, but in doses of 100 to 400 mg, procainamide produced significant and progressively dose-related increases in His-Purkinje system refractoriness. Suppression of some types of ventricular arrhythmia by small doses of this drug may be explained by changes in refractoriness of the His-Purkinje system produced by doses of procainamide as small as 100 mg.

Time dependent changes in the functional properties of the atrioventricular conduction system in man

Time dependent changes in the electrophysiological properties of the atrioventricular conducting system (AVCS) were determined at two or more cycle lengths (CL) in 22 patients using bundle of His (H) electrograms, incremental atrial pacing and atrial extrastimulus method. The atrioventricular (A-H interval) and intraventricular (H-V interval) conduction times and refractory periods (RP) of the atrium, the A-V node (AVN) and His-Purkinje system (HPS) were measured during the control period, and repeat measurements were made after a 30 minute interval in eight patients (group A), after a 60 minute interval in nine (group B) and after 30 and 60 minute intervals in five (group C). No statistically significant changes from control values were seen after 30 and 60 minute intervals in any group in sinus rate, A-V nodal conduction time and the onset of A-V nodal Wenckebach block. H-V intervals were identical to the control values in all groups. Insignificant changes from control values occurred in RP of the atrium and HPS. Only the functional refractory period (FRP) of the AVN showed a statistically significant decrease from control values in groups B and C. This decrease could be explained by changes in autonomic tone. These observations in general confirm the reproducibility of electrophysiological properties of AVCS within one hour, and further support the validity of the techniques utilized in this and previously reported studies in the evaluation of cardioactive drugs.

Echocardiographic manifestation of "false" mitral stenosis that was

An unusual normal posterior direction of motion of the posterior mitral valve leaflet echo during diastole was detected in a patient whose clinical and hemodynamic data confirmed the presence of significant rheumatic mitral stenosis after other conditions causing echocardiographic pattern of "false" mitral stenosis were ruled out. The finding of normal direction of motion of the posterior mitral valve leaflet when associated with abnormal EF slope of the anterior mitral valve leaflet does not rule out the existence of significant mitral stenosis.

Induction of atrioventricular nodal reentrant tachycardia after atropine. Report of five cases

After intravenous administration of 0.5 mg of atropine sustained atrioventricular (A-V) nodal reentrant tachycardia could be produced in five patients who had no prior historical or electrocardiographic evidence of supraventricular tachycardia. During the control period single atrial echo beats could be demonstrated in four of the five patients, but no instance of sustained tachycardia occurred. Atropine, known to enhance A-V nodal conduction, allowed achievement of longer A-H intervals (Case 1) and provided the necessary balance of conduction and refractoriness within the A-V nodal reentrant pathways (Cases 1 to 5) to sustain A-V nodal reentry in these patients.

The gap phenomena during retrograde conduction in man

Ventricular refractory period studies were performed in 12 consecutive and unselected patients using the ventricular extrastimulus method (V 2 ) at basic ventricular cycle lengths (V 1 V 1 ). In six of 12 patients two types of retrograde gaps occurred. At relatively long V 1 V 2 intervals, ventriculo-atrial (V-A) conduction failed and then resumed at shorter V 1 V 2 intervals. The initial sites of retrograde block were the A-V node in two patients and the His-Purkinje system in four patients. In both groups, resumption of V-A conduction at shorter V 1 V 2 intervals occurred because of retrograde delay within the His-Purkinje system. Retrograde gaps differ from previously described antegrade gaps in A-V conduction: The site of initial block in A-V gaps is the His-Purkinje system and resumption of A-V conduction occurs at shorter A 1 A 2 intervals because of proximal delay in the A-V node (type I) or delay in the proximal His-Purkinje system (type II). In V-A gaps the site of initial block may be either the A-V node or the His-Purkinje system and resumption of V-A conduction always occurs due to delay within the distal His-Purkinje system. A common feature of both A-V and V-A gaps is the fact that delay of the more premature impulses allows time for previously refractory areas to recover excitability and both can be functional in nature. Only one of the 12 patients had both A-V and V-A gaps in conduction. Retrograde gaps in V-A conduction are more commonly observed than A-V gaps.

Intraventricular conduction delay as a determinant of atrial echo beats

Re-entry within the atrioventricular (A-V) node is a common cause of atrial echo beats and paroxysmal atrial tachycardia. This report deals with observations made in four patients in whom the determining factor for atrial echo beats appeared to be a critical conduction delay occurring within the His-Purkinje system and not within the A-V node. The evidence in support of this conclusion is as follows: 1) at a constant A-V nodal delay, echo beats only occurred when a critical His-Purkinje delay was reached; 2) in the presence of different intraventricular conduction times, atrial echoes were dependent on a requisite His-Purkinje conduction delay; 3) at variable A-V nodal conduction times, echo beats appeared only when a requisite delay in His-Purkinje conduction developed; 4) at a constant premature coupling interval atrial echo beats could be abolished when refractoriness within the His-Purkinje system was decreased by decreasing the cycle length of the basic drive; and 5) at constant A-V nodal conduction times, a reciprocal relationship existed between the magnitude of the His-Purkinje delay and the "echo interval" defined as the interval between the onset of ventricular depolarization and the echo beat.