Haemodynamic findings in experimental right ventricular ischaemia after right coronary arterial ligation

Acute ischaemia limited to the free wall of the right ventriclewas produced by right coronary arterial ligation (RCAL) in 20dogs. Contrast M-mode and cross-sectional echocardiography wasperformed in 7 cases to investigate the presence of tricuspidinsufficiency. The haemodynamic findings obtained with an openpericardium at 15 to 30 min showed increases in right (l.20.5to 2.70.7 mmHg, P0.01) andleft (5.0 0.8 to 6.60.9 mmHg, P005)ventricular end-diastolic pressures, and decreases in heartrate (1394.9 to 1195.1 bpm, P0.01), cardiac index (1066.6 to817.3 ml min^–1 kg^–1, P001), stroke index (79 6 to72 8 ml x 100 beat^–1 kg^–1, P0.02), right (23.8l.5to 19.41.5 mmHg, P0.01) and left (1097.2 to 958.2 mmHg, P005)ventricular systolic pressures and right ventricular strokework index (18.32.4 to 11.41.8 g m kg^–1, P0.01). In 6of 15 cases the 'y' descent became deeper than the 'x' descentin right atrial pressure (RAP). Tricuspid insufficiency gradeI–II/IV was present in 3 of 7 cases, 2 of them with a'y'>'x' in RAP. Right ventricular mechanical alternans, probablysecondary to a decrease in contractility, appeared in 10 of20 cases after RCAL. Closure of the pericardium exaggeratedthe haemodynamic alterations and a dip-plateau appeared in 2cases on the right ventricular pressure curve. We conclude thatsignificant aemodynamic alterations in right ventricular functionare produced by RCAL in dogs, and they are exaggerated afterclosing the pericardium.     

Lack of correlation between haemodynamic and cardiopulmonary exercise capacity improvement after catheter-balloon mitral valvuloplasty

The long-term effects of percutaneous transvenous mitral commissurotomyon exercise capacity and ventilation were investigated to determinewhether a dissociation between haemodynamic improvement andexercise capacity increase occurs in patients with mitral stenosis.Eighteen patients aged 45 ± 12.3 years (mean ±SD) with symptomatic mitral stenosis performed a symptom-limitedbicycle exercise test while respiratory gases were measuredbefore and 6 months after percutaneous transvenous mitral commissurotomy.The mitral valve area increased from 1.07 ±0.22 to 1.98±0.67 cm². P<0.0001 and the mean mitral gradient decreasedfrom 12.9 ±4.5 to 5.3±4.8mmHg, P<0.001, withouta significant increase in cardiac output index (from 2.64 ±0.55 to 2.77 ± 0.56 l. min_{– 1}. m_{– 2}, P= ns).This haemodynamic improvement was still present at the 6-monthfollow-up catheterization. Mean exercise workload and peak oxygenuptake increased 6 months after percutaneous transvenous mitralcommissurotomy from 88.3 ± 28.1 to 97.8 ± 25.1watts, P= 0.01, and from 18.1 ± 5.3 to 19.9 ±4.8 ml. kg_{– 1}.min_{– 1}, P<0.05. Total ventilation,ventilatory equivalents and oxygen pulse at the end of the exercisetest remained unchanged Correlations between peak oxygen orexercise capacity improvement and mitral valve area increasewere poor (r= 0.27, P= ns, r= 0.24, P=ns). This clear dissociationbetween haemodynamic improvement and improvements in minor exercisecapacity after percutaneous transvenous mitral commissurotomysuggests that peripheral alterations persist. Future studiesin which patients are trained after valvuloplasty may be helpful.     

Biplane transoesophageal echocardiography, transthoracic Doppler, and magnetic resonance imaging in the assesment of coarctation of the aorta

This study compared flow-sensitive magnetic resonance imagingwith biplane transoesophageal echocardiography in combinationwith continuous wave Doppler from the suprasternal notch inpatients with native coarctation or after surgical repair. Twenty patients (mean age 33 years, range 17–60) wereinvestigated, of whom 15 had undergone surgery at mean age 13years, range 5.43. Peak and mean flow in the ascending and descendingaorta as well as coarctation peak velocity were determined withthe magnetic resonance imaging phase contrast technique. Coarctationpeak velocity was also measured by Doppler from the jugulum.Magnetic resonance imaging axial sections as well as biplanetransoesophageal echocardiography were used to measure the smallestdiameter of the constricted segment. Sixteen healthy volunteers,mean age 36 years, range 22.63, provided reference values formagnetic resonance imaging determined volume of flow in theaorta. Peak flow in the descending aorta was 9.2 ±3.71.min ^{– 1} (reference 130 ± 2.5, P<0.01) and meanflow 3.1 ±0.9 I. min^{– 1} (reference 3.4 ±0.8,P>0.05). The ratio of descending-to-ascending peak flow was0.54 ±0.17 (reference 0.69 ± 0.10, P<0.01)and mean flow 0.68 ± 0.15 (reference 0.69 ± 0.08,P>0.05). The coarctation velocity was slightly higher withDoppler than with magnetic resonance imaging (+ 0.24 ±0.44 m. s^{– 1}, 95% confidence interval +0.45 to + 0.02m.s^{– 1}, P= 0.05). The coarctation diameter was slightlylarger with magnetic resonance imaging than with transoesophagealechocardiography (1.4 ±3.5 mm, 95% confidence interval+ 3.1 to – 0.3 mm, P= 0.11). Both methods are suitable for the assessment and follow-up ofcoarctation of the aorta Flow assessment with magnetic resonanceimaging provides a hitherto unavailable measure with which toassess the severity of obstruction.     

Rapid diminution of calcium in the myocardium by transfer to pericardial solutions: Myocardial dialysis

A new method is described for the controlled and specific depletionof calcium from the vascularly perfused heart of experimentalanimals by means of dialysis, using a pericardial solution. A 30–40ml isotonic phosphate buffer pH7.3 with a low Ca²⁺ and high Mg²⁺ concentration (0.2 and 2.7mM respectively) wasinserted into the pericardial cavity of anaesthetized dogs andkept therefor 10 or 60 min. The calcium content of the subendocardialand subepicardial halves of the left ventricular wall was similarlydecreased to about 70% (P<0.01) within 10 min and to 62%(P<0.001) at 60 min, compared to that of hearts dialysedfor60 min in a standard solution ofCa²⁺ 1.2 mM and Mg²⁺ 1 mM.Calcium content of the myocardium dialysed with low Co²⁺ anda standard Mg²⁺ solution decreased to only 75% (P<0.01)at 60 min. Similar changes of calcium were measured in otherparts of the heart. An increase in Co²⁺ concentration in the pericardial solutionwas observed at the same time as a decrease in calcium in themyocardium. The increase in Ca²⁺ reached about 0.7 mM at 60min, but decreased slightly, and finally, fell to 85% of pre-dialysisvalues at 60 min. It is concluded that this method of myocardial dialysis is effectivein reducing myocardial calcium and is influenced by the durationof dialysis and the Mg²⁺ content of dialysate.     

Apical ballooning syndrome, emotional stress and women: reply

In our systematic overview, we found that apical ballooningsyndrome is preceded by an emotional stressor in 27% of casesand by a physical stressor in 38%.¹ uli suggests that emotionalstress may be a more frequent trigger, especially in women.Indeed, in his meta-analysis     

Evaluation and prognostic significance of left ventricular diastolic function assessed by Doppler echocardiography in the early phase of a first acute myocardial infarction

AIM: To study the prognostic significance of left ventricular diastolicfunction evaluated by transmitral and pulmonary venous flowvelocities obtained in the early phase of a first acute myocardialinfarction in relation to later development of congestive heartfailure. METHODS: Pulsed Doppler echocardiography of transmitral and pulmonaryvenous flow was assessed in 65 consecutive patients with a firstmyocardial infarction within 1 h of arrival in the coronarycare unit. RESULTS: A univariate regression analysis identified age, left ventricularejection fraction 45%, mitral E deceleration time 130 ms, E/Aratio >1·5, peak pulmonary venous atrial flow velocity30 cm . s^–1 and a difference between mitral and pulmonaryvenous atrial flow duration >0 ms as variables significantlyrelated to the development of congestive heart failure. However,in a multivariate analysis only mitral E deceleration time 130ms and age were significant independent variables related tothe development of congestive heart failure during the firstweek following a first acute myocardial infarction. CONCLUSION: Assessment of left ventricular diastolic function complementsmeasurements of systolic function in the evaluation of cardiacfunction, and mitral deceleration 130 ms best identifies patientsat risk of development of congestive heart failure followingacute myocardial infarction.     

Cardiac responses to hypoxia and hypercapnia in spinal man

The purpose of this study was to evaluate the effect of interruptionof the descending supraspinal sympathetic outflow on heart ratecontrol during exposures to chemical stimuli. We investigatedthe heart rate responses to progressive isocapnic hypoxia andhyperoxic hypercapnia using the rebreathing technique and quantifiedthe relationship between heart rate (HR), oxygen saturation(SaO₂), alveolar PCO₂ (P_ACO₂), and minute ventilation (V_E) in16 chronic tetraplegic subjects with low cervical spinal cordtransection. The HR responses were determined from the linearslopes of HR on SaO₂ and HR on P_ACO₂. We found that mean restingheart rate was within normal range; 66 ±3 (SEM) beatsmin^–1. HR increased as oxygenation fell or CO₂ tensionrose. The mean tetraplegic HR/SaO₂ was 0.83 ± 0.14 beatsmin^–1 per 1% fall in SaO₂ and that of HR/P_ACO₂ was 0.30± 0.13 beats min^–1 per mmHG rise in P_ACO₂. TheHR and V_E responses to either hypoxia or hypercapnia were relatedin the tetraplegic subjects. We conclude that the stimulatoryHR reponses to chemical stimuli are not suppressed by cervicalspinal cord transection. Thus, the descending sympathetic activitydoes not underlie the HR acceleration by chemical stimuli.     

Use of changes in ST segment elevation for prediction of infarct artery recanalization in acute myocardial infarction

Background: The role of the ECG in evaluating reperfusion statusafter thrombolytic treatment in acute myocardial infarctionis not clear. Dramatic ST segment changes have been observedduring recanalization of an infarct-related artery, but ST criteriahave not been definitively established for prediction of coronaryartery patency. Differences in ST segment changes in relationto infarct localization have not been evaluated, and furtherinvestigation is required into reciprocal ST depression, whichprovides information independent from ST elevation. Therefore,the aim of this study was to evaluate how early changes in STsegment elevations and depressions predict vessel patency afterfibrinolysis for patients with anterior and inferiorllateralinfarcts. Methods and Results: Two hundred patients with a Pardee wavein the ECG and chest pain of less than 6 h duration were giventhrombolytic treatment. The result of the therapy was assessedsimultaneously with coronary angiography. Patients were dividedinto two groups: I (50 patients) without recanalization (TIMIgrade 0, 1 or 2), and II (150 patients) with successful recanalization(TIMI grade 3). Before and after therapy, analysis of the 12lead ECG included maximum ST elevation measurement (H₁, H₂ respectively),the sum of ST elevations (H₁, H₂), the sum of ST segment depressions(h₁, h₂), and the ratios of ST segment changes (R₁ = H₂:H₁,R₂ = H₂:H₁, R₃ = h₂:h₁). The mean interval from the first tothe second ECG was 3.5 ± 1 h. Successive values of R₁and R₂ were examined to find that which best distinguished betweenthe two groups. The best values for prediction of reperfusionwere: (1) For anterior wall infarct Specificity Sensitivity R₁ 0.6 83.3% 88.7% R₂ 0.5 83.3% 92.0% (2) For inferior and lateral infarct R₁ < 0.5 100% 93.8% R₂ < 0.5 100% 92.8% In 13 patients with a complete right or left bundle branch blockin the first or second ECG, the result of treatment was predictedin 11 patients using criteria for factor R₁ and in 12 patientsusing criteria for R₂ Analysis of ST segment depressions revealed a significant correlationbetween normalization of ST segment depressions and elevations(R₃ vs R₁: r = 0.60, P < 0.05; R₃ vs R₂ r = 0.59, P <0.05). Multivariate discriminant analysis showed an independentvalue of R₃for discrimination between the two groups, but onlyin patients with inferiorllateral infarcts. The overall accuracyof the common algorithm in predicting reperfusion was significantlybetter in patients with inferiorllateral infarcts (Chi² test,P = 0.0078). When separate algorithms were used, there was nosignificant difference between patients with anterior or inferiorllateralinfarcts because of the significant improvement in predictionof reperfusion in patients with anterior infarcts (McNemar'stest: P = 0.041). Conclusions: We conclude that analysis of ST segments on thestandard 12-lead ECG offers valuable help in the early identificationof successful recanalization of infarct-related arteries afterthrombolytic therapy in patients with acute myocardial infarction.Use of the ratio of ST segment normalization according to theseparate criteria for anterior and inferiorllateral infarctsgives the test a high sensitivity and specificity, even in thepresence of interventricular conduction disturbances.     

Balloon occlusion during coronary angioplasty as a model of myocardial ischaemia: reproducibility of sequential inflations

In order to evaluate the potential of balloon occlusion duringcoronary angioplasty as a model of myocardial ischaemia in manwe have measured coronary sinus blood flow (CSBF), myocardialoxygen consumption (MVO₂), lactate extraction (LER) and electrocardiographicchanges in 11 patients undergoing left anterior descending artery(LAD) angioplasty. Baseline measurements were made before ballooncrossing and between inflations. Four consecutive inflationseach of 60 s duration were made; 5 min return to baseline wasallowed between inflations. There was a significant reduction in CSBF and MVO₂ (ml min^–1)during inflations 2, 3 and 4 (CSBF: 121±6694±53,113±4999±42, 124±66102±41, P<0.02;MVO₂:11.3±6.6–9.1±3.9, 10.4±3.7–8.7±2.4,12.2±4.49.4±2.8, P<0.05). However during thefirst period of balloon occlusion there were inconsistent changesin coronary flow with an overall rise in mean flow (97±35128±80ml min^–1, P = NS) and an overall rise in mean myocardialoxygen consumption (9.6 ± 3.812.5 ± 7.5 ml min^–1,P = NS). There was lactate production during all four inflationsbut the changes during the first one did not achieve statisticalsignificance. These inconsistent changes during the first inflation were thoughtto be due to partial obstruction of the stenosis by the deflatedballoon before primary dilatation. The changes due to crossingand during the first two inflations were further investigatedin another group of 12 patients undergoing LAD angioplasty.Great cardiac vein flow (GCVF), CSBF, MVO₂ and LER were recordedat baseline, during crossing and during the first two inflations.With the deflated balloon across the stenosis there were nochanges in CSBF or MVO₂ but there was a fall in GCVF (103±2877±50,P = NS) and a significant fall in LER (77±5716±37,P<0.01). Although there was a fall during the first inflationin CSBF, GCVF, MVO₂ and lactate extraction none of these changeswere significant. During the second inflation these changeswere of greater magnitude and achieved statistical significance. While balloon occlusion during coronary angioplasty has thepotential of providing a model of ischaemia in man we have foundthe first inflation period unreliable, due to the variable degreeof occlusion by the deflated balloon. We suggest that only subsequentinflations after the primary dilatation are used for observations.These findings are of significance when evaluating the effectsof therapeutic interventions during PTCA. Various refinementsin measurements of the effects of ischaemia will improve thespecificity of the model.     

Lipoprotein(a) as a risk predictor for cardiac mortality in patients with acute coronary syndromes

Aims Raised lipoprotein(a) concentrations are considered to be arisk factor for atherothrombotic diseases. We examined whetherbaseline concentrations were a risk factor for an adverse outcomein patients admitted with acute coronary syndromes. Methods and Results Five hundred and nineteen patients admitted with suspected acutecoronary syndromes were studied and followed prospectively fora median of 3 years. The prognostic significance of a baselinelipoprotein(a) concentration of 30mg.dl^–1or lower forsubsequent cardiac death was assessed in patients with myocardialinfarction (266) and unstable angina (197) and compared withother variables in regression models. In patients with myocardialinfarction, a baseline lipoprotein(a) concentration of 30mg.dl^–1wasassociated with a 62% increase in subsequent cardiac death comparedto the lower concentration group (29·8% vs 18·6%,Log rankP=0·04). In a multivariate regression model abaseline lipoprotein(a) concentration of 30mg.dl^–1retainedits significance as an independent predictor of cardiac death(P=0·037). In patients with unstable angina, baselineconcentrations of 7·9mg.dl^–1were found to be significantpredictors of cardiac death in univariate (P=0·021) andmultivariate (P=0·035) regression models. Conclusion Baseline lipoprotein(a) concentrations in patients admittedwith acute coronary syndromes are associated with an increasedrisk of cardiac death. For patients with myocardial infarctiona concentration of 30mg.dl^–1appears appropriate as a riskdiscriminator; for patients admitted with unstable angina, however,much lower concentrations of lipoprotein(a) appear to be prognosticallyimportant.     

Autonomic balance in patients with angina and a normal coronary angiogram

The pathophysiology of angina pectoris in patients with a normalcoronary angiogram is not clear. Furthermore, the pathophysiologicalimpact of ST changes in syndrome X is controversial. The purposeof this study was to investigate cardiac autonomic function,by measuring 24 h heart rate variability, in patients with andwithout electrocardiographic evidence of ischaemia during exercise. Thirty-two patients with angina pectoris, a normal coronaryangiogram, echocardiogram, hyperventilation test and gastro-oesophagealinvestigation were studied. Fourteen healthy subjects servedas controls. Fifteen patients had significant ST segment depressionduring stress testing, whereas 17 had no electrocardiographicsigns of ischaemia. Heart rate variability was calculated as(1) mean RR= mean of all normal RR intervals, (2) the differencein mean RR level between when awake and when asleep (mean RRwake-sleep)—a tentative index of sympathetic activation,(3) the standard deviation (SD)—a broad band measure ofautonomic balance, and (4) a percentage of successive RR intervaldifferences 6% (pNN6%)—an index of vagal modulation. Thecoronary vascular resistance was measured at rest and duringpacing. Mean RR and autonomic indexes did not differ between patientswith a positive exercise test and controls (831/884 m 24 h SD125/134 m pNN6% 6.715.4%, respectively). Patients with a normalexercise test had shorter mean RR (758 ms vs 844 m P<0.05)and significantly reduced 24-h SD (103 ms vs 134 m P<0.05)than controls, whereas values for vagal index (6.5% vs 5.4%)did not differ from healthy controls. Mean RR wake-sleep alsotended to be lower in patients with a normal exercise test (–125 ms vs – 173 ms) compared to controls (P<0.1). Patientswith a positive exercise test had a significantly attenuatedreduction in coronary vascular resistance during pacing in comparisonto patients with a normal exercise test (–0.131–0.26mmHg x min. ml^{– 1}; P<0.05). The findings suggest the occurrence of general elevated sympatheticactivation in angina patients with a normal exercise test. Patientswith a positive exercise test exhibited no signs of autonomicdysfunction although these patients had altered coronary vascularresistance indicating microvascular angina. This supports thesuggestion that patients with a normal exercise test constitutean independent pathophysiological entity.     

Factors explaining the under-use of reperfusion therapy among ideal patients with ST-segment elevation myocardial infarction

Aims To determine the relative impact of time to hospital arrival,baseline cardiovascular risk (i.e.TIMI mortality risk index),intracerebral haemorrhage risk, and comorbid disease burdenon the likelihood of not receiving reperfusion therapy amongST-segment elevation myocardial infarction (STEMI) patientswithout contraindications to treatment. Methods and results Retrospective population-based cohort of3994 patients admitted to 103 acute care hospitals with chestpain and STEMI within 12 h of symptom onset in Ontario,Canada, between 1999 and 2001. Patients with one or more documentedabsolute or relative contraindication (n=909) were excludedfrom the analyses. Reperfusion therapy was defined as the receiptof either fibrinolysis or primary percutaneous coronary intervention.Multivariable analysis and likelihood ² was used to quantifythe importance of each factor in predicting the non-utilizationof therapy. In total, 23.1% of patients received no reperfusiontherapy. Listed in order from greatest to least importance,predictors of non-utilization of reperfusion therapy includedincreasing time to hospital presentation (likelihood ² 31.6,P<0.001), higher intracerebral haemorrhage risk (likelihood² 27.1, P<0.001), higher baseline cardiovascular risk (likelihood² 25.4, P<0.001), and greater number of chronic comorbidconditions (likelihood ² 15.4, P<0.001). The importance ofeach factor on non-utilization was independent, additive, notexplained by age effects alone, or driven by subgroups traditionallyunder-represented in clinical trials. Conclusion Care gaps in the use of reperfusion therapy widenwith both increasing baseline cardiovascular risk and increasingintracerebral haemorrhage risk. Future studies should examinewhether the implementation of clinical decision tools whichallow for more accurate risk–benefit tradeoff predictionsimprove the treatment gaps when using life-saving therapiesin this patient population.     

Right and left ventricular ejection fraction and left ventricular volume changes at rest and during exercise in normal subjects

The effect of exercise upon right and left ventricular ejectionfractions (RVEF and LVEF) as well as the changes upon left ventricularend-diastolic and end-systolic volume indices (LVEDVI and LVESVI)were investigated. Twenty-two normal subjects were studied atrest and during upright submaximal exercise. RVEF was determinedusing a first-pass method. LVEF was measured using multiplegated blood pool imaging. During the exercise test ECGs remained normal. HR and BP increasedsignificantly (P<0.01). RVEF increased from 44%±4(mean±SD) to 60%±6 (P<0.001). LVEF increasedfrom 62%±6 to 76±5 (P<0.001). A wider scatterwas observed in RVEF than in LVEF. There was a 14% increasein LVEDV-index and a 14% decrease in LVESV-index (P<0.001).A multiple regression analysis with RVEF as the dependent variableand HR, systolic BP, LVEF, LVEDV-index and LVESV-index as independentvariables showed a significant correlation between RVEF andLVEF and systolic BP (P<0.05). Our data provide insight intothe mechanisms by which the pump performance is increased innormal subjects. The central mechanisms observed are the Starlingeffect and an increase in contractility of the myocardium. Thisis connected in the general circulation to an increase in afterload,indicating a redistribution of blood from the vascular bedsto the muscles and to the heart.     

Reassessment of the relation between QRS forces of the orthogonal electrocardiogram and left ventricular ejection fraction

Previous studies have demonstrated the existence of a strongpositive correlation between the amplitude of QRS forces ofthe orthogonal electrocardiogram and the angiographically determinedleft ventricular ejection fraction. In a large group of patientsevaluated for chest pain, we examined the relationship betweenthe arithmetic summation of R_x+R_y+Q_z (R) the maximal and meanspatial QRS vectors and the ejection fraction (EF). In a totalof 252 patients, there was a statistically significant correlationbetween R and EF but a low correlation coefficient value (r:0.22, P<0.001). This relationship was essentially due tothe group of patients with coronary artery disease and myocardialinfarction (r: 0.24, P<0.015) whereas there was no correlationin the group of normal subjects or in patients with coronaryartery disease without myocardial infarction. In the group withmyocardial infarction, a significant correlation between R andEF existed only in patients with anterior myocardial infarction(r: 0.41, P<0.025). In conclusion, both ejection fractionand amplitude of QRS forces decrease in coronary artery diseaseespecially when an anterior myocardial infarction is present.However, despite the positive association between these angiographicand electrocardiographic indices, the low value of the correlationcoefficient indicates that it is not possible to predict ejectionfraction from the value of R in individual patients.     

Mean 24 hour heart rate, minimal heart rate and pauses in healthy subjects 40-79 years of age

In order to establish normal limits for mean 24 h heart rate(_t and pauses, 24 h ambulatoryECG recordings from 260 healthy subjects 40–79 years ofage were analysed. The _24h varied from 53 to 95beats/min (mean±2 s.d.: 74±I8 beats/min). Theminimal _t varied from 36 to78 beats/min (mean± 2 s.d.: 56 ±16 beats/min).Analysis of variance showed an additive effect of smoking, sex,leisure-time physical activity and age on both _t, and the effect of the three first factors wasstatistical significant at the 1% level for both heart ratevariables. The males, the non-smokers and the physically activesubjects had a lower _24h anda lower minimal _t than females,smokers and passive subjects. Older subjects had a lower _t was non-significant. A total of 77 subjects (30%) had a pause (R-R interval1500 ms),but in only 12 (5%) did the pause exceed 1750 ms with the longestpause measuring 2040 ms. Further analysis of the longest pausein each of the 77 subjects with pauses showed that 46 of thelongest pauses occurred at night following a gradual decreasein the R-R intervals for a few beats (‘post-accelerationpauses’). In 12 subjects the longest pause was causedby sinus arrest, and in nine cases a blocked atrial prematurebeat was thought to be present. Wenckebach A- V block was seenin only two subjects. It is concluded that sex, age, smoking and leisure-time physicalactivity are all factors that have to be considered for a thoroughevaluation of heart rate variables in the 24 h ambulatory ECG.     

Inferior ST segment depression as a useful marker for identifying proximal left anterior descending artery occlusion during acute anterior myocardial infarction

To determine whether or not ST segment deviation on admissionelectrocardiograms can identify patients with anterior acutgemyocardial infarction due to proximal left anterior descendingartery occlusion, the magnitude and location of ST segment elevationor depression were compared between patients with proximal leftanterior descending artery occlusion (group A, n=47) and thosewith distal left anterior descending artery occlusion (groupB, n =59). ST segment depression in each of the inferior leadswas significantly greater in group A than in group B. The incidenceof ST segment depression 1 mm in each of the inferior leads(II; 81% vs 27%, III; 85% vs 54%, aVF; 87% vs 47%, P<0.01)was significantly higher in group A than in group B. In addition,the incidence of ST segment depression 1 mm in all of the inferiorleads was significantly greater in group A than in group B (77%vs 22%, P<0.01). In group A, maximal ST segment elevationwas more frequent in lead V alone (43% vs 14%, P<0.01). GroupA had greater ST segment elevation in lead a VL than group B,and the incidence of ST segment elevation 1 mm in lead a VLwas significantly higher in group A than in group B (66% vs47%, P<0.05). ST segment depression 1 mm in all of the inferiorleads was most valuable for identifying group A patients (77%sensitivity and 78% specificity). In contrast, the maximal STsegment elevation in lead V₂ alone or ST segment elevation 1 mm in lead a VL had a low diagnostic value (43% sensitivityand 86% specificity, 66% sensitivity and 53% specificity, respectively).In conclusion, this study indicates that analysis of ST segmentdeviation in the inferior leads is useful for identifying patientswith acute anterior myocardial infarction due to proximal leftanterior descending occlusion.     

Protective effect of beta-blockade on dipyridamole-induced myocardial ischaemia: Role of heart rate

This study was designed to investigate the effect of heart ratechanges on dipyridamole echocardiographic tests in patientswith coronary artery disease treated with propranolol. We prospectively studied 12 patients (8 men and 4 women; meanage 56.5 ± 8.7 years) selected by: (a) angiographic evidenceof significant coronary artery disease; (b) adequate echocardiographicwindow; (c) positive dipyridamole echocardiography test resultsin baseline conditions (step I); (d) test reproducibility inthe absence of treatment; (e) negative dipyridamole echocardiographytest results after 7 days of treatment with propranolol (120mg. day^–1) in twice divided doses daily (step II). In all patients treated with propranolol, dipyridamole echocardiographictesting was repeated 24 h after the last negative test. In thesepatients, transoesophageal atrial pacing was performed at peakdipyridamole infusion to increase heart rate to values similarto those observed at baseline (step III). At baseline, heartrate and rate-pressure product were significantly lower in patientstreated with propranolol (–20.3% and –22.5% in groupII, P<0–001 vs step I; –24.3% and –26.4%in group III, P<0.05 vs step I), but the different treatmentsdid not produce significant differences in systolic and diastolicblood pressure. At peak dipyridamole infusion, heart rate andrate-pressure product increased with either placebo or propranololtreatments with respect to baseline, while remaining significantlylower with propranolol as compared to placebo ( –29.6%and –29.5% in step II, P<0001). During treatment withpropranolol plus transoesophageal pacing to maintain heart rateat values attained with placebo, the rate-pressure product didnot change significantly with respect to placebo, nor did systolicblood pressure. Transoesophageal atrial pacing performed duringpropranolol treatment to restore heart rate to baseline valuesdid not affect the dipyridamole echocardiographic test in eightpatients (group I), and induced transient wall abnormalitiesin four patients (group II) (P=ns). Our data suggest that the anti-ischaemic effect of propranololin man is not correlated only to reduction of heart rate.     

Detection of acute myocardial infarction by a new, sensitive and rabid method for determination of creatine kinase B-subunit activity

An immunoinhibition method for the assay of creatine kinase(CK) isoenzymes by continuous monitoring of the ATP formationin the CK reaction by a purified firefly luciferase reagenthas been developed. The sensitivity of the firefly assay ofATP makes it possible to assay CK-B subunit activity (CK-B)in serum down to 1 U/l. In healthy individuals CK-B varied between 2 and 12, mean 3U/l. A wide range of CK-B activity was observed after acutemyocardial infarction (AMI), intramuscular injection and surgerywith overlapping between these different categories. Thereforethe maximal change in CK-B activity (CK-B) was studied in 98patients admitted to a coronary care unit. In all 57 patientswithout a subsequent diagnosis of AMI according to conventionalcriteria CK-B was < 5 U/l. In all 41 patients with AMI CK-Bwas 5 U/l. In all healthy individuals CK-B was < 2 U/l.CK-B 5 U/l was found after i.m. injection and different kindsof surgery in three out of 60 patients. Thus, the present method for determination of CK activity hasbeen shown to possess high precision in low activities, to beas rapid as conventional methods and to be simple enough tobe used in a routine laboratory. With these properties the methodshould be suited for early diagnosis and early exclusion ofeven very small AMIs.