RS Complex Research Articles

A new criterion to diagnose wide-complex tachycardia: The quest for a simple, efficient diagnostic marker

Wide complex tachycardia (WCT) is a rhythm disturbance with a heart rate 100 beats/min and QRS duration 120 ms. An accurate and timely diagnosis of the underlying rhythm is crucial because the most common cause of WCT is ventricular tachycardia, and inappropriate treatment can lead to devastating consequences. The differential diagnosis of WCT includes supraventricular tachycardia (SVT) with pre-existing or functional bundle branch block (BBB), pre-excitation, drug- and electrolyte-induced QRS widening, and ventricular tachycardia. 1,2 A bewildering number of electrocardiographic (ECG) criteria and other stepwise algorithms have been described for the differential diagnosis of regular WCTs. ECG guidelines using QRS morphology, QRS duration, QRS axis, atrioventricular dissociation, fusion beats, absence of precordial RS complex, QRS concordance, presence of initial R wave in lead aVR, and estimation of initial and terminal ventricular activation velocity ratio (vi/vt) have been reported with varying degrees of sensitivity and specificity. 3-6 Most of the existing morphologic criteria favoring ventricular tachycardia have been noted to be present in a substantial number of patients with intraventricular conduction defect (IVCD) during sinus rhythm as described by Alberca et al. 7 The algorithms are complex, use multiple steps, and often require expert judgment and are still prone to errors. In this edition of the Journal, Pava et al 8 propose a new simple criterion to discriminate VT from SVT in patients with WCT. They analyzed 218 wide complex tachycardia

Left Bundle Branch Block—Significance of the Spatial QRS Axis (Vector)

An electrocardiogram (ECG) of an 82-year-old woman (see Figure 1) showed complete left bundle branch block (LBBB: QRS duration 148ms), left axis deviation to -52o, rS complexes in V1–V6, absence of septal Q-waves, and first-degree atrioventricular block (PR 236ms).

ECG Criteria to Identify Epicardial Ventricular Tachycardia in Nonischemic Cardiomyopathy

ECG criteria identifying epicardial (EPI) origin for ventricular tachycardia (VT) in nonischemic cardiomyopathy have not been determined. Endocardial (ENDO) and EPI basal left ventricle fibrosis characterizes the VT substrate. We assessed the QRS from 102 basal-superior/lateral EPI and 67 comparable ENDO pace maps in 14 patients with nonischemic cardiomyopathy. Pace mapping focused on low bipolar voltage areas. Published morphology criteria: q wave in lead I (QWLI) and no q waves in inferior leads and interval criteria: pseudo-delta wave > or =34 ms, intrinsicoid deflection time > or =85 ms, shortest RS complex > or =121 ms, and maximum deflection index > or =0.55 were assessed for ability to identify EPI origin. Sixteen EPI and 8 ENDO of the 34 mapped VTs (71%) in the study population and 14 EPI and 7 ENDO VTs from an 11-patient validation cohort were localized to basal-superior/lateral left ventricle and corroborated pacing data. A QWL1 was seen in EPI but not ENDO pace maps (91% versus 4%; P<0.001), identified 14 of 16 EPI VTs (sensitivity, 88%), and was seen in 1 of 8 ENDO VTs (specificity, 88%). None of the remaining criteria achieved similar sensitivity without specificity <50%. We identified 4 criteria (q waves in inferior leads, pseudo-delta wave > or =75 ms, maximum deflection index > or =0.59, and QWL1) having > or =95% specificity and > or =20% sensitivity in identifying EPI/ENDO origin for pace maps. This 4-step algorithm identified the origin in 109 of 115 pace maps (95%), 21 of 24 VTs (88%) in the study population, and 19 of 21 VTs (90%) in validation cohort. Morphological ECG features that describe the initial QRS vector can help identify basal-superior/lateral EPI VTs in nonischemic cardiomyopathy.

Evolution of a pseudo-control region in the mitochondrial genome of Palearctic buzzards (genus Buteo)

Sequences of the mitochondrial genome were employed to study the phylogenetic relationships of the Palearctic buzzards (genus Buteo). In a first approach a 2.5 kb PCR fragment comprising the section between ND6 and 12s genes was isolated from Buteo buteo hureo, cloned and sequenced. The gene order corresponds to the novel arrangement described for Folco peregrinrrs by Mindell et al. (1998). The fragment includes a non coding section between the /RNA G ' and /RNAPh' genes consisting of a 338 bp nonrepetitive section followed by a cluster of 23 tandem repeats with a unit length of 48 bp. Since this noncoding section seems to be the remnant of an ancestral duplicated control region, it was named pseudo-control region (YCR). For the phylogenetic investigation a highly variable 205 bp subsection of the YCR was analysed from 31 specimens comprising the species Buteo buteo, Burro rufinus, Buteo oreopllilus, Buteo llemilosius, and Buteo lrigopus. Comparison of the 31 VCR sequences revealed 18 different haplotypes, which can be divided into six distinct groups. The haplotypes of B. liemilosius and B. Iagopus are clearly separated, the same is true for the haplotypes of the subspecies B. b. japonicus. Although the haplotypes of B. rufinus are found in a separate clade (with two clusters), this clade contains also four specimens of B. buteo and B. oreophilus. The remaining cluster contains taxa from the buteo and ~ulpinus groups as well as three specimens of B. o. trizonatus. According to our data the YCR appears as an appropriate marker sequence for differentiation at the species level. Within the B. buteolB. rufinuslB. oreophil~rs complex the status of B. rufinus, and perhaps B. b. joponicus, as a separate species is underlined. In contrast, the species status of B. oreophilus seems debatable. No unambiguous genetic differentiation was found among the subspecies, with the exception of B. b.,jripo~~icus.

Mean and variability of QT-interval: Relevance to psychiatric illness and psychotropic medication

Byline: Rahul. Kumar, Chaitra. Ramachandraiah, Pratap. Chokka, Vikram. Yeragani The QT interval conceptually represents the duration from the onset of depolarization to the completion of repolarization of the cardiac cycle. On a standard ECG, it is measured from the beginning of the QRS complex (or RS complex if there is no Q wave) to the end of the T wave. This interval has been considered as a surrogate of action potential duration. The QT interval is slightly longer in women than in men, is affected by autonomic tone as well as catecholamines, and it shows circadian variations. The most important aspect of this interval is its relation with heart rate (the reciprocal of inter-beat-interval).[sup] A large number of formulae have been proposed to establish a rule allowing conversion of a pair of QT and R-R durations into a standardized QTc value corresponding to a basal R-R interval of 1 second. Bazett's formula is the most commonly used. Normally the QTc is between 350 to 430 milliseconds. Now there is substantial amount of evidence as to the electrophysiology and how changes in autonomic function can affect the function of the heart. [sup] [1],[2],[3],[4],[5],[6] The main myocardial cell type that determines the QT interval is the 'M' cell type. The cardiac action potential is generated by the changing transmembrane permeability to ion currents such as Na[sup] + , Ca[sup] 2 + and K[sup] + . Like all living cells, the potential inside a myocyte is negative compared to the outside. However, cardiac cells are excitable and when appropriately stimulated, the ion channels within the cell membrane open and close sequentially. This changes the transmembrane ion permeability and leads to the sequential development of the transmembrane potential that is called the action potential. The initial depolarization (phase 0) is triggered by the rapid inward sodium (INa) and the L- and T-type calcium currents (ICa-L and ICa-T), which change the cell potential from - 90 to 30 mV. The transient outward Ito potassium current is responsible for the slight repolarization immediately after the overshoot (phase 1). During the following plateau phase (phase 2), the cell potential is maintained by a balance between the inward L-type calcium current (ICa-L) and the electrogenic sodium-calcium exchange current (INaCa), and the outward Ito current. The repolarization phase (phase 3) of the myocyte is driven predominantly by outward movement of potassium ions, carried as the rapid (IKr) and slow (IKs) components of the delayed rectifier potassium current. The diastolic depolarization (phase 4) results from a combination of the decay of the outward delayed rectifier IKr and IKs currents, which maintains the resting potential at approximately - 90 mV, and the activation of the inward pacemaker current (If) and the inward sodium background leak current (INa-B). A variety of other different potassium channel subtypes are also present in the heart. Cardiac arrhythmias reflect disturbances of impulse initiation or impulse propagation. These consist of conduction blocks, reentrant rhythms and dysfunction of sino-atrial (SA) node and disturbances that originate from various ectopic foci. Paroxysmal ventricular tachycardia is the result of an ectopic focus in the ventricles and can be associated with bizarre QRS complexes in the ECG. This is much more serious than a paroxysmal supraventricular tachycardia as paroxysmal ventricular tachycardia could lead to ventricular fibrillation. Fibrillation is an irregular contraction and is ineffectual in propelling blood. In the ventricles, the vulnerable period coincides with the down slope of the T wave, and when a premature impulse arrives during the vulnerable period, this may lead to fibrillation. This may become self-sustaining due to reentrant process of cardiac excitability. Tricyclic antidepressants (TCAs) have profound effects on cardiovascular system due to their strong autonomic effects and also a quinidine-like effect on cardiac conduction. …

Clinical Use of Electrocardiography in Adults With Congenital Heart Disease

The prevalence of adult congenital heart disease (ACHD) has risen markedly over the past 2 decades, with the number of adults now rivaling the number of children with severe defects.1 This is, perhaps, not surprising given that current care allows nearly 90% of infants born with heart defects to thrive into their adult years.1,2 This remarkable triumph is tempered, however, by the realization that early interventions were reparative and not curative. Numerous complications may surface years after uneventful childhood courses, justifying vigilant clinical follow-up throughout adulthood. The 12-lead ECG remains an invaluable cornerstone in the clinical appraisal of adults with congenital heart disease that, in certain circumstances, provides diagnostic and/or prognostic information. The present review imparts a clinical perspective to ECG interpretation in ACHD, emphasizing practical and pathogenomonic findings in the more frequently encountered congenital defects in adults. Anatomic features of the conduction system relevant to ECG findings in ACHD are summarized, including variations in the location of the sinus node, atrioventricular (AV) node, and His-Purkinje system. Thereafter, pertinent ECG features are highlighted for common subtypes of ACHD (Table). Examples are provided throughout for illustration. View this table: Table. Typical ECG Features in Common Forms of ACHD ### Sinus Node In the morphologically normal heart, a crescent-shaped sinus node is characteristically located epicardially along the lateral aspect of the superior cavoatrial junction. It generates a P-wave axis typically between 15° and 75°. Most patients with ACHD have normally positioned atrial chambers, called atrial situs solitus, with normal sinus node location. The position of the sinus node may, however, vary with the atrial chambers and their appendages. #### Juxtaposition of the Atrial Appendages In juxtaposition of the atrial appendages, both appendages are on the same side of the arterial pedicle rather than each being ipsilateral to its respective atrium. Left juxtaposition, with left-sided atrial appendages, frequently accompanies tricuspid atresia and has …

Site-specific twelve-lead ECG features to identify an epicardial origin for left ventricular tachycardia in the absence of myocardial infarction

Identification of an epicardial origin for left ventricular tachycardia (LV-VT) based on electrocardiogram (ECG) criteria facilitates the approach to catheter ablation. Reported criteria, although helpful, may not apply uniformly to all LV regions. We hypothesized that unique region-specific ECG patterns identify epicardial LV-VTs in patients without myocardial infarction. The QRS morphologies during pace mapping from 402 epicardial and 234 comparable endocardial sites and 19 epicardial VTs were analyzed in 15 patients with respect to morphology and duration of all and components of the QRS. Basal superior (N = 244) and apical superior (N = 141) pace mapping sites showed Q wave in lead I more commonly from epicardial vs corresponding endocardial sites (90% vs 16%, 88% vs 26% respectively; P <.001). The absence of Q wave in leads II-III-aVF identified epicardial basal superior sites, P = .002. Basal inferior (N = 140) and apical inferior (N = 76) epicardial sites showed Q wave in leads II-III-aVF (81% vs 37%, 92% vs 33%, P <.001). These morphologic criteria identified 16 of 19 VTs. The QRS duration was longer from the epicardium, 213 +/- 45 ms vs 191 +/- 41 ms, P <.001, although significant overlap existed. Reported criteria (pseudodelta wave > or =34 ms, intrinsicoid deflection time > or =85 ms, and shortest RS complex > or =121 ms) were region specific in their ability to identify epicardial origin, with some criteria not having value in specific regions and sensitivity/specificity varying from 14% to 99% and 20% to 94%. ECG features distinguishing epicardial LV-VT are site specific, including the presence or absence of a Q wave in leads that reflect local ventricular activation.

A new algorithm in the differential diagnosis of wide complex tachycardia

A correct electrocardiographic diagnosis of the mechanism of a wide complex tachycardia (WCT) is important when instituting emergent therapy and for long-term prognostic and therapeutic considerations. While any algorithm has the risk of oversimplifying a complex problem, it is absolutely essential to have an initial strategy for the acute evaluation of an arrhythmia. Causes of wide QRS tachycardia include (1) supraventricular tachycardia (SVT) with pre-existing or functional bundle branch block, including sinus tachycardia, atrial tachycardia, atrial flutter, atrial fibrillation (AF) and AV nodal re-entry tachycardia, (2) orthodromic circus movement tachycardia with pre-existing or functional bundle branch block, (3) SVT with conduction over an accessory pathway, (4) Antidromic circus movement tachycardia using an accessory pathway in the anterograde direction and AV node in the retrograde direction, (5) ventricular tachycardia, and (6) ventricular paced rhythm. Ventricular tachycardia is by far the commonest underlying mechanism of WCT.1 The overall goal of any algorithm is to make things simpler yet effective. Most criteria are based on QRS complex duration, QRS axis, concordant pattern, presence of Q-waves, AV dissociation, fusion beats, absence of precordial RS complex, QRS alternans, and presence of multiple wide complex morphologies. Starting in 1978, several criteria have been developed to aid in the diagnosis of WCT. For evaluation of RBBB morphology tachycardias,Wellens et al .2 proposed (1) duration of QRS > 140 ms, (2) left-axis deviation, (3) certain configurational characteristics of QRS, and (4) atrioventricular (A-V) dissociation as the criteria for … *Corresponding author. Tel: +1 617 632 7393; fax: +1 617 632 7620. E-mail address : mjoseph2{at}caregroup.harvard.edu

Twelve-lead ECG features to identify ventricular tachycardia arising from the epicardial right ventricle

Usefulness of 12-lead ECG for predicting an epicardial origin for ventricular tachycardia (VT) arising from the right ventricle (RV) has not been assessed. An epicardial approach is sometimes warranted to eliminate RV VT. The purpose of this study was investigate the hypothesis that specific ECG features identify an epicardial origin for RV VT. To mimic an endocardial or epicardial origin, we paced representative sites in 13 patients undergoing RV endocardial/epicardial mapping (134/180 pace map sites). QRS duration from epicardial vs endocardial sites was not different (183 +/- 27 ms vs 185 +/- 28 ms, P = .3). Reported cut-off values for identifying epicardial left ventricular origin, pseudo-delta wave (> or =34 ms), intrinsicoid deflection time (> or =85 ms), and RS complex (> or =121 ms) did not apply to the RV. A Q wave in lead II, III, or aVF was more likely noted from inferior epicardial vs endocardial sites (53/73 vs 16/43, P <.01). A Q wave in lead I was more frequently present from epicardial vs endocardial anterior RV sites (30/82 vs 5/52, P <.001). QS in lead V(2) was noted from anatomically matched epicardial anterior RV sites (22/33 vs 13/33, P <.05). In the RV outflow tract, no ECG feature distinguishing epicardial/endocardial origin reached statistical significance. A Q wave or QS in leads that best reflect local activation suggest an epicardial origin for RV depolarization and may help in identifying a probable epicardial site of origin for RV VT. QRS duration and reported criteria for epicardial origin of VT in the left ventricle do not identify a probable epicardial origin in the RV.

Electrocardiographic recognition of the epicardial origin of ventricular tachycardias.

Some ventricular tachycardias (VTs) originating from the epicardium are not suitable for endocardial radiofrequency ablation and require an epicardial approach. The aim of this study was to define the ECG characteristics that may identify an epicardial origin of VTs. We analyzed the 12-lead ECG recordings during epicardial and endocardial left ventricular pacing in 9 patients to verify the hypothesis that the epicardial origin of the ventricular activation widens the initial part of the QRS complex. Then, we analyzed the ECG pattern in 14 VTs successfully ablated from the epicardium after a failed endocardial approach (group A), in 27 VTs successfully ablated from the endocardium (group B), and in 28 additional VTs that could not be ablated from the endocardium (group C). Four distinct intervals of ventricular activation were defined and measured: (1) the pseudodelta wave, (2) the intrinsicoid deflection time in V2, (3) the shortest RS complex, and (4) the QRS complex. VTs from groups A and C showed a significantly longer pseudodelta wave, intrinsicoid deflection time, and RS complex duration compared with VTs of group B. There was no difference between groups A and C. A pseudodelta wave of > or =34 ms has a sensitivity of 83% and a specificity of 95%, an intrinsicoid deflection time of > or =85 ms has a sensitivity of 87% and a specificity of 90%, and an RS complex duration of > or =121 ms has a sensitivity of 76% and a specificity of 85% in identifying an epicardial origin of the VTs. ECG suggests VTs originating from the epicardium and those with an unsuccessful radiofrequency ablation from the endocardium.

Unipolar waveforms and monophasic action potentials in the characterization of slow conduction in human atrial flutter.

Anisotropic propagation may be involved in the development of areas of slow conduction in atrial flutter. We evaluated monophasic action potentials (MAPs) and simultaneous unipolar (0.2-400 Hz) and bipolar electrograms from multiple atrial sites of patients undergoing RF ablation of idiopathic atrial flutter. Nine patients (mean age 46 +/- 20 years) with typical atrial flutter (one with both types) were studied. Unipolar electrograms with triphasic complexes of small amplitude and with a slow, negative deviation of the baseline preceding the rS deflection indicated transversal conduction in relation to the orientation of cardiac fibers; smooth rS complexes longitudinal conduction; QS complexes onset of activation; and R complexes end of activation or collision. In all patients with typical atrial flutter, slow conduction occurred in the corridor between the inferior vena cava, the tricuspid annulus, and the coronary sinus. Transversal conduction was observed in this area, whereas the remaining sites showed longitudinal conduction. Anatomically guided RF ablation was successful in five patients. Transversal conduction was recorded in all successful sites. In the patient with atypical atrial flutter, slow conduction was noted in the high lateral right atrium, also exhibiting transversal conduction. Ablation at this area terminated the arrhythmia. All the areas of transversal conduction during flutter displayed longitudinal conduction after restoration of sinus rhythm. MAPs were normal in all patients during atrial flutter and sinus rhythm, even at the areas where transversal conduction was recorded. These findings suggest that anisotropic propagation is involved in the genesis of functionally determined areas of slow conduction during typical atrial flutter.

Chronopotentiometric Determination of Aluminum by Solochrome Violet RS

A reliable and very sensitive derivative adsorption chronopotentiometric method for the determination of trace amounts of aluminum, based on the adsorptive accumulation of its solochrome violet RS complex on the HMDE, was developed in this paper. Experimental conditions were optimized including solution pH value, ionic strength, concentration of solochrome violet RS, preconcentration potential and preconcentration time. The linear working range was 0.27 ± 27 μg/1. The detection limit was 0.14 μg/1 and the relative standard deviation was 1.7% μg/1 Al. This method was applied to the determination of Al in real water samples. Comparison of the proposed method to the voltammetric mode and other ligands is presented.

Evaluation of the specificity of morphological electrocardiographic criteria for the differential diagnosis of wide QRS complex tachycardia in patients with intraventricular conduction defects.

Although several ECG criteria have been described for the differential diagnosis of tachycardias with a wide QRS complex, their applicability in patients with preexisting intraventricular conduction defects (IVCDs) has been questioned. The specificity of previously described criteria in this context is unknown. We analyzed prospectively the specificity of the QRS morphological criteria previously described in ECGs during sinus rhythm of 232 patients with IVCD. Only 5 of 12 analyzed criteria had a specificity > or = 0.90 among our patients: (1) a triphasic configuration (Rsr' or Rr') QRS complex in V1 in the presence of a right bundle-branch block morphology (BBBM); (2) a QS, QR, or R QRS pattern in V6 in the presence of a right BBBM; (3) any Q in V6 in the presence of a left BBBM; (4) a concordant pattern in all precordial leads; and (5) the absence of an RS complex in all precordial leads (particularly useful for left BBBM). The following criteria--QRS duration > 140 ms; a left axis with right BBBM, right superior axis with right BBBM, monophasic or biphasic R wave in V1 with right BBBM, and a relation R/S < 1 with right BBBM; an R > 30 ms in lead V1 or V2 with left BBBM, > 60 ms from QRS onset to S nadir with left BBBM, a notched downstroke S wave with left BBBM, and an R-to-S interval > 100 ms in one precordial lead--had a specificity of 0.43, 0.54, 0.87, 0.80, 0.85, 0.78, 0.66, 0.69, and 0.63 (0.84 in right BBBM), respectively. Most of the previously described morphological criteria favoring ventricular tachycardia are present in a substantial percentage of patients with IVCD during sinus rhythm. These findings suggest a limited applicability of these criteria in this subset of patients.

Polarographic determination of yttrium based on reduction of its solochrome violet RS complexApplication to the analysis of the superconductor YBa 2Cu 3O y

A practical method for the polarographic determination of yttrium is described. The procedure is based on the reduction of the yttrium-solochrome violet RS (SVRS) complex. Experimental conditions include the use of Triton X-100 in order to achieve good separation of the Y-SVRS and SVRS peaks. Application of the procedure to the determination of yttrium as a major component in the superconductor YBa 2Cu 3O y gave good results.

Determination of iron(III) and titanium(IV) as their Solochrome Violet RS complexes by constant-current stripping potentiometry: Part 1. Automated single-point calibration method for iron(III)

An automated constant-current stripping potentiometric method for the determination of iron(III) as its Solochrome Violet RS complex is described. The instrumentation is based on a stripping potentiometry unit, a sample changer, a burette system and a conventional three-electrode system with a mercury film electrode. The method can be utilised over a large concentration range [0–500 μg 1−1 iron(III)], by an automated adaption of the experimental conditions to the concentrations found in the samples. A single-point calibration procedure with calibration for three different concentration ranges is used. The possibility for normalisation of the electrode response to compensate for variations in hydrodynamic conditions and electrode area is demonstrated. Using this normalisation, the reproducibility is better than 5% for samples at the 15 μg 1−1 iron(III) level. For higher concentrations (65 and 300 μm 1−1), the corresponding values are 2.9 and 3.5%, respectively. The applicability of the method for the determination of titanium(IV) is discussed. The method is applied to the determination of iron(III) in tap water and rain water samples.

Determination of iron(III) and titanium(IV) as their Solochrome Violet RS complexes by constant-current stripping potentiometry: Part 2. Partial least-squares regression calibration procedure for iron(III) and titanium(IV)

An automated method for the determination of iron(III)_ and titanium(IV) as their Solochrome Violet RS complexes by constant-current stripping potentiometry and partial least-squares (PLS) regression calibration is described. The multivariate calibration procedure overcomes the problem of completely overlapped titanium(IV) complex and reagent stripping peaks and allows prediction of iron(III) and titanium(IV) concentrations from data obtained under non-linear response conditions. For iron(III), accuracy and precision at the 15 and 65 μg 1−1 concentration levels are 13.2 ± 2.1 mg 1−1 (16%) and 67.5 ± 4.6 mg 1−1 (6.8%), respectively. For titanium(IV) the corresponding values are 14.6 ± 7.3 mg 1− (50%) and 69.5 ± 7.9 (11%). Limitations in the applicability of PLS to electrochemical stripping applications are discussed.

Electrocardiographic responses to carbon monoxide and cyanide in the conscious rat

Carbon monoxide (CO) and cyanide (CN), commonly found in exhaust fumes and smoke, act as hypoxic agents in eliciting morbid and lethal effects. This study explored the effects of these two toxicants on the ECG in a controlled and well-characterized animal model. Levine-prepared awake female rats were treated with 1500 and 2400 ppm CO for 90 min, CN at 4 mg kg , or 1500 ppm CO plus 4 mg kg CN. As in past studies, CO initially induced hyperglycemia and many-fold increases in blood lactate concentration, and rebound increases in blood glucose during recovery. CN produced hyperglycemia, however, there was no glucose rebound, nor was there a significant increase in lactate. CN plus 1500 ppm CO produced glucose changes similar to that of CO alone. CO exposure also induced hypothermia and hypotension, while CN produced little change in these parameters. CO increased heart rate, while CN tended to decrease heart rate. PR interval was increased significantly 4.5–17.0 ms by exposure to CO, with or without combination with CN, while CN alone produced minimal change in the PR interval. QT interval was increased up to 20 ms by exposure to CO, with or without combination with CN. CN alone produced no change in the QT interval. T wave duration was increased up to 22.5 ms by exposure to 1500 ppm CO, with or without combination with CN. CN alone produced minimal changes in T wave duration. There were no changes in duration of the (Q)RS complex or of the R wave. QT interval lengthening was positively correlated with the decrease in systolic blood pressure (0–30 min, r = 0.657, P < 0.05; 0–60 min, r = 0.704, P < 0.05). Hypothermia was correlated with increase in lactate concentration ( r = 0.73, P < 0.05) and with decrease in blood pressure ( r = 0.69, P < 0.05). No correlation between body temperature and QT interval was observed. The results indicate that CO at the concentrations used in the Levine-prepared rat has major effects on the ECG in slowing AV conduction and ventricular repolarization. In contrast, CN at 4 mg dl has little or no effect on either conduction or repolarization in this animal model. These findings are discussed in light of past animal and human studies.

Determination of aluminum in human cerebrospinal fluid through the electrochemical and spectroscopic properties of its complex formed with Solochrome Violet RS

Aluminum present in pooled samples of cerebrospinal fluid is essentially uncomplexed since it may be determined by differential pulse polarography of the Al: Solochrome Violet RS (SVRS) complex. The aluminum may also be determined spectrophotometrically through its depression of the SVRS absorbance at 600 nm at pH 8.4. The Al:SVRS ratio in the complex is 1:2.

QRS complex changes in the V 5 ECG lead during cardiac surgery

The QRS complex in lead V5 was studied during cardiac surgery. R wave amplitude decreased after induction of anesthesia to approximately 50% to 60% of the preanesthetic level before the institution of CPB ( P < 0.001). An rS complex appeared immediately after cardioversion and changed in configuration to an Rs complex 15 to 30 minutes after aortic declamping. The R wave continued to recover toward the preanesthetic level at sternal closure. Patients with coronary artery disease had a poorer recovery of the R wave ( P < 0.05) than patients with valvular heart disease; the former recovered to only 50% of the preanesthetic level at sternal closure. Nonsurvivors had much smaller R waves (26.1 t 20.5%) than survivors ( P < 0.001). The R wave peaked 30 to 40 ms after initiation of the QRS complex, which indicates recovery of conductivity and the activation sequence of the left ventricular (LV) free wall, which is easily disturbed by hypothermia, cardioplegia, and ischemia during aortic cross-clamping. Monitoring QRS complex changes in lead V5 appears to be important on weaning from cardiopulmonary bypass to detect regional ischemia, and also to observe electrophysiologic recovery of the LV free wall.

Cathodic stripping voltammetry of vanadium based on adsorptive accumulation of its solochrome violet RS complex at the static mercury drop electrode

AbstractA very sensitive electrochemical stripping procedure for vanadium is reported. Accumulation is achieved by controlled adsorption of the vanadium/solochrome violet RS complex on the static mercury drop electrode. Optimal experimental parameters found include an accumulation potential of −0.22 V, solochrome violet RS concentration of 2.0 × 10−6M, and a differential pulse stripping mode. After 5 minutes preconcentration, a detection limit near 1.7 × 10−10 M vanadium is obtained. The response is linear over the 0–21 μg1−1 concentration range, and the relative standard deviation (at the 11.2 μg1−1 level) is 3.8%. The possible interference by other trace ions are investigated. Simultaneous determination of vanadium with molybdenum and cadmium is illustrated. The merits of this procedure are demonstrated in the analysis of sea and river waters.