The major cystic fibrosis causing mutation exhibits defective propensity for phosphorylation

The major cystic fibrosis causing mutation, F508del-CFTR (where CFTR is cystic fibrosis transmembrane conductance regulator), impairs biosynthetic maturation of the CFTR protein, limiting its expression as a phosphorylation-dependent channel on the cell surface. The maturation defect can be partially rescued by low-temperature (27°C) cell culture conditions or small-molecule corrector compounds. Following its partial rescue, the open probability of F508del-CFTR is enhanced by the potentiator compound, VX-770. However, the channel activity of rescued F508del-CFTR remains less than that of the Wt-CFTR protein in the presence of VX-770. In this study, we asked if there are allosteric effects of F508del on the phosphorylation-regulated R domain. To identify defects in the R domain, we compared the phosphorylation status at protein kinase A sites in the R domain of Wt and F508del-CFTR. Here we show that phosphorylation of Ser-660, quantified by SRM-MS, is reduced in F508del-CFTR. Although the generation of a phosphomimic at this site (substituting aspartic acid for serine) did not modify the maturation defect, it did enhance F508del-CFTR channel function after pharmacological rescue with corrector VX-809, and treatment with the potentiator, VX-770. These findings support the concept that defective phosphorylation of F508del-CFTR partially accounts for its altered channel activity at the cell surface.

Functional Rescue of F508del-CFTR Using Small Molecule Correctors

High-throughput screens for small molecules that are effective in “correcting” the functional expression of F508del-CFTR have yielded several promising hits. Two such compounds are currently in clinical trial. Despite this success, it is clear that further advances will be required in order to restore 50% or greater of wild-type CFTR function to the airways of patients harboring the F508del-CFTR protein. Progress will be enhanced by our better understanding of the molecular and cellular defects caused by the F508del mutation, present in 90% of CF patients. The goal of this chapter is to review the current understanding of defects caused by F508del in the CFTR protein and in CFTR-mediated interactions important for its biosynthesis, trafficking, channel function, and stability at the cell surface. Finally, we will discuss the gaps in our knowledge regarding the mechanism of action of existing correctors, the unmet need to discover compounds which restore proper CFTR structure and function in CF affected tissues and new strategies for therapy development.

Identification and validation of hits from high throughput screens for CFTR modulators

These are exciting times with the appearance of small molecule compounds in clinical trials which target the basic defects caused by mutation in the CFTR gene. This progress was enabled by years of basic research probing the molecular and cellular consequences caused by mutation and the development of methods by which to study the primary anion transport defect in a high-throughput manner by robotics. Future progress with the development of new, more effective corrector compounds is needed. Such discovery will require further progress in defining the molecular targets for effective intervention using a multidisciplinary approach, merging computational, molecular, proteomic and cell biological methods. There is also an urgent need to develop means to link the right therapeutic compound to the right patients given the heterogeneity of the CF patient population. We envision a time when mid to high-throughput methods will be married with stem cell biology to enable testing a compendium of compounds on cells derived from each individual patient. Given the rate of progress in this field- this scenario may exist in the not too distant future.

Molecular basis for the ATPase activity of CFTR

CFTR is a member of the ABC (ATP binding cassette) superfamily of transporters. It is a multidomain membrane protein, which utilizes ATP to regulate the flux of its substrate through the membrane. CFTR is distinct in that it functions as a channel and it possesses a unique regulatory R domain. There has been significant progress in understanding the molecular basis for CFTR activity as an ATPase. The dimeric complex of NBD structures seen in prokaryotic ABC transporters, together with the structure of an isolated CF-NBD1, provide a unifying molecular template to model the structural basis for the ATPase activity of CFTR. The dynamic nature of the interaction between the NBDs and the R domain has been revealed in NMR studies. On the other hand, understanding the mechanisms mediating the transmission of information from the cytosolic domains to the membrane and the channel gate of CFTR remains a central challenge.

[Atrial flutter: causes, electrophysiological characteristics, treatment with radiofrequency catheter ablation]

Atrial flutter (TP) is one of the most common supraventricular tachyarrhythmias. Because of its influence on hemodynamics of the circulation, prolonged episode of paroxysmal TP can lead in as many as 1/3-1/2 patients to clinical signs of coronary insufficiency, decompensation of the circulatory system, or even such life-threatening states, like cardiac arrest. Patients with preexcitation syndrome, hyperthyroidism, as well as children, whose atrio-ventricular (AV) node can conduct in a 1:1 fashion, are in the group of particularly high risk of complications. Recurrent episodes of TP are also associated with frequent occurrence of thromboembolic events. Based on the electrocardiographic (ECG) pattern TP is divided into common type, with negative "sawtooth" in leads II, III, aVF, and uncommon type, which is characterised by other ECG morphologies. Experimental and clinical data have revealed, that common and some part of uncommon type are due to clockwise or counterclockwise reentry in the right atrium. These forms of TP can be treated with high success-rate with radiofrequency (CR) ablation. Because of difficulties in pharmacological conversion of the arrhythmia to the sinus rhythm and high frequency of recurrences, CR ablation seems to be a high effective method of treatment in patients with common and some forms of uncommon TP.

[Radiofrequency ablation of accessory pathway's atrial insertion site]

Brought into clinical practice in 80, method of radiofrequency catheter ablation (RFCA) enabled possibility of causative treatment in patients with preexcitation syndrome. RFCA may be performed utilizing various techniques, choice of one of them depends on experience and preference of the operator. Aim of the study was assessment of efficacy and safety of RFCA targeting accessory pathway's atrial insertion site with help of unipolar signals from ablation-catheter with regard to various localizations of accessory pathways. Material and method studied population consisted of consecutive 149 patients with symptomatic, drug-resistant WPW-syndrome, which were admitted to our Center for electrophysiologic study and RFCA. From the studied population two groups were subdivided: patients with left-sided (group I, n = 112) and right-sided (group II, n = 37) accessory pathway. Every patient underwent electrophysiological study with use of four diagnostic electrodes and after preexcitation was confirmed RFCA was undertaken. In case of left-sided accessory pathway transseptal puncture was performed. Analyzed parameters were: total duration, fluoroscopy-time, number of current-applications during RFCA, as well as success-rate, complications and recurrences after successful ablation. Patient in both groups did not differ significantly with respect to age and sex. Success-rate was insignificantly higher in gr.I (92.8%) than in gr.II (86.5%), as was RFCA-duration (136.4 min versus 123.6 min). We found significant differences in fluoroscopy-time, which was longer in gr.I (37.2 min versus 28.4 min, p < 0.05). Complications occurred in 1 patient in each group. RFCA aiming at accessory pathway's atrial insertion site with use of unipolar tracings from ablation-catheter is safe and effective method of treatment in WPW-patients.

[Tachycardia-induced cardiomyopathy]

Dilated cardiomyopathy induces circulatory insufficiency with poor prognosis. Persistent tachyarrhythmias may be the cause of this disease. At particular high risk for heart damage and insufficiency are young people and children. The group of most dangerous arrhythmias consist of: incessant tachycardia in patients with preexcitation syndrome and supraventricular tachyarrhythmias (atrial flutter and fibrillation, ectopic atrial tachycardia) with high rate of ventricles. The result of arrhythmias is dilatation of the heart and thinness of ventricular walls with hemodynamic disorders. The effective therapy of arrhythmias--ablation of the accessory pathway in patients with pre-excitation syndrome or reversion to sinus rhythm (pharmacological or electric cardioversion) in patients with atrial fibrillation and flutter, often leads to normalisation of heart ejection function and diameter. Therefore it exist important question: is dilated cardiomyopathy the cause or consequence of tachyarrhythmias? Causative antiarrhythmic therapy in these second cases gives a possibility to improve the prognosis in patients with such a disease.

[Measurement dispersion of the QT interval and its significance in different diseases]

QT dispersion reflects in homogenecity of ventricular repolarization. It is calculated using 12-leads standard synchronized ECG or 24-hours Holter monitoring. The most common used indicators are: QT dispersion (QTd), based on Bazett's formula corrected for heart rate QT dispersion (QTcd) and QT dispersion ratio (QTdR). QT apex and QTd corrected for total number of leads ECG in which QT interval was counted are rare used. Increased QT dispersion is observed among others: following myocardial infarction (MI), coronary heart disease (CAD), hypertension, chronic heart failure (CHF), long QT syndrome, as well as diabetes. Following mentioned diseases increased QT dispersion has prognostic value for sustained ventricular tachycardia. Dispersion of repolarization > or = 80 ms after MI is a risk factor for sudden cardiac death. Following acute MI decrease of QT dispersion after successful thrombolytic therapy is observed and its value > or = 100 ms is regarded as a marker of reperfusion insufficiency. QT dispersion in patients with CAD correlates with extent of ischemia and decreases after coronary angioplasty (PTCA). In recent years beneficial effect of angiotensin-converting enzyme inhibitors and beta-adrenolytic therapy on QT dispersion was described. Actually the improvement of computerised methods in assessment of QT dispersion is observed, but it require further investigations.

[Use of intravascular ultrasonography (IVUS) for diagnosis and treatment of coronary artery disease--case report]

One of the additional methods of coronary artery assessment is intravascular ultrasound (IVUS). Contrary to coronary angiography this relatively new technic provides new information including precise calculations of stenosis degree, morphology of atheromatous plaque and differentiation of its structure. Coronary angiography was performed in 54 years old male patient with unstable angina, revealing 99% stenosis in distal RCA. Discrepancy between clinical presentation and angiographic findings and exercise test resulted in performing IVUS of LAD. Angiographically clear LM and LAD were found to be narrowed 52% and 58% on IVUS. Subsequent CABG resulted in symptoms withdrawal and increase of physical tolerance. Exercise test after CABG did not reveal ischaemia in area of LCA at 10 METs. IVUS is found to be an important technic in assessment of silent or ambiguous lesions and in many cases allows to choose the optimal method of treatment of coronary artery disease.

[Dispersion of the QT interval in unstable angina pectoris]

Increased dispersion of the QT interval is a risk factor of sudden cardiac death. In unstable angina pectoris (UA) a few authors described QT dispersion. The aim of the study was to assess QT dispersion in patients with UA in comparison to the healthy subjects and analysis QT dispersion according to the presence during in-hospital stay significant cardiac events like: death due to cardiological causes, myocardial infarction and urgent revascularization. Study group consisted of 54 patients with UA in a class IIIB of Braunwald classification (18 women, 36 men, mean age: 58.2 +/- 9.6 years). In 40 patients after pharmacological treatment stabilization in the first three days of hospitalization was achieved and during in-hospital stay significant cardiac events were not observed--group I. In 14 patients during in-hospital stay significant cardiac events were present, including 5 death due to cardiological causes--group II. During first two days of hospitalization coronary angiography was performed in all patients. The control group comprised 25 healthy subjects (8 women, 17 men, mean age 56.4 +/- 6.1 years). On admission to the hospital in all patients and in control group, using standard 12-leads ECG, following parameters were calculated: QT dispersion (QTd), corrected QT dispersion based on Bazett's formula (QTcd) and QT dispersion ratio (QTdR). In the study group as well as in group I and II values of QTd, QTcd and QTdR were significantly higher than in healthy subjects. In group I all the QT parameters were significantly lower than in group II (QTd: 56.8 +/- 11.2 vs 68.6 +/- 16.6 ms, p = 0.002). The highest value of QT dispersion was found in patients who died during in-hospital stay and it was significantly higher than in survivors (86.0 +/- 13.4 vs 57.1 +/- +/- 10.6 ms, p = 0.004). A cut-off value for QTdR > or = 9% identified patients with high risk of sudden cardiac death.

CONCLUSIONS

QT dispersion analysis in unstable angina pectoris allows to distinguish patients according to the risk of sudden cardiac death. Patients with high risk of sudden cardiac death identify the best QTdR.

[The assessment and clinical significance of heart rate variability]

Heart rate variability (HRV) is a phenomenon to generation through the sinus node consecutive impulses in the different succession. HRV is regarded as a marker of autonomic nervous system tone of the heart. To assess HRV following methods: time domain, frequency domain and non-linear analysis are known. Time domain parameters correlate with frequency domain parameters. Some parameters can be used substitution, particularly reflect parasympathetic activity: rMSSD, pNN50 and HF. In clinical practice the most useful is time domain analysis based on 24-hours ecg Holter monitoring. Among time domain parameters the most significant prognostic value has SDNN. Decreased HRV following many diseases has been described. Significant prognostic value of decreased HRV after myocardial infarction (MI) and in patients with chronic heart failure (CHF) has been proved. Decreased HRV after MI is independent as well as ejection fraction (EF) sudden cardiac death risk factor. In patients with SDNN value below 50 ms high risk of cardiac death is observed. SDNN should be estimated on 7th day of MI to evaluate patients with high risk of sudden cardiac death. In patients after MI with ventricular tachycardia (VT) before VT decreased HRV is described. During MI beneficial influence of infarct-related artery patency on HRV is observed. HRV correlates with EF and infarct site too. HRV in patients with CHF correlates with EF and functional severity of CHF. Correlation between decreased HRV and increased mortality in CHF has been shown. In diabetic patients decreased HRV is observed. Following diabetes examination of HRV is useful to estimate early phase of autonomic neuropathy. Increase HRV parameters is observed in the course of beta-adrenolytic and converting enzyme inhibition treatment. In other diseases, including heart transplantation prognostic value of HRV and its clinical significance are still investigated.

[Radiofrequency catheter ablation of two accessory pathways in patients with WPW Syndrome]

In 10-30% patients with WPW syndrome more than one accessory pathway in electrophysiology study is observed. These patients make a group of higher atrial fibrillation and coming next ventricle fibrillation risk. We present the 39 years old patient with symptomatic WPW syndrome, without preexcitation signs in ECG at rest. In medical history--palpitations was observed from childhood with one episode of atrial fibrillation with high ventricle response required cardioversion. Electrophysiology study: without preexcitation signs at rest, two ortodromic AV reentrant tachycardias were induced--200 and 166/min. Two accessory pathways were diagnosed, left lateral and left midseptal. Radiofrequency catheter ablation of both accessory pathways was made during tachycardia, first lateral, next septal. In six month follow-up the patient was asymptomatic.

[Right ventricular infarction]

Right ventricle infarction (RVI) is not a rare clinical entity. It complicates approximately half of inferolateral myocardial infarctions. Under the term RVI we can find mild, asymptomatic dysfunction of right ventricle and cardiogenic shock as well. RVI is associated with increased mortality and its presence obliged us to qualify patient to a high risk group. Diagnosis is based on clinical signs, electrocardiographic findings, hemodynamic measurements and echographic evaluations. The proper treatment of RVI requires support of right ventricle preload with fluid administration, maintainance of atrio-ventricular synchrony, reduction of right ventricle afterload. Early reperfusion with fibrinolytic therapy and coronary angioplasty should be regarded as the prior methods of treatment RVI. Patients who survive RVI have complete resolution of hemodynamic abnormalities with restoration of proper right ventricle function.

[Arrhythmogenic dysplasia of the right heart ventricle]

Arrhythmogenic right ventricular dysplasia (ARVD) is a heart muscle disease in which muscle tissue has been partially replaced by adipose or fibro-adipose tissue. Morphologic changes in the right ventricle and ventricular arrhythmias are characteristic. Pathomorphological changes should be confirmed by NMR or endomyocardial biopsy. Morphological changes ought to be found by ultrasound methods or angiographic examination. ECG exercise test, Holter monitoring, late potentials, total ventricular activation time and programmed stimulation of right ventricle are used to evaluate the risk of sudden death due to ventricular arrhythmias which is the most important problem. Those methods indicate pharmacologic or invasive therapy (RF ablation, implanted cardioverter-defibrillators), and are used to establish the effectiveness of treatment.

[Cardiomyopathy in diabetes. Ultrastructural examinations]

The functional and morphological changes in myocardium of diabetic patients is caused by diabetic macroangiopathy, diabetic microangiopathy, autonomic neuropathy and metabolic disorders. Mechanism of these changes in the course of diabetes is not fully known. To determine whether there are myocardial ultrastructure differences between patients with diabetic cardiomyopathy (normal coronary angiograms) and diabetic patients with coronary artery disease, electron microscopy examination were performed of 70 sections received from seven biopsied patients (1F, 6M), average age 53 years (range: 42-60) with diabetes type II WHO (group A) without clinical evidence of prior coronary artery disease and hypertension, and 100 sections from 10 patients (2F, 8M), average age 54 years (range: 42-65) with diabetes and coronary atherosclerosis. These patients had clinical evidence of heart failure and were submitted to bypass-graft operations (group B). Endomyocardial biopsy tissues were obtained from the right ventricle without complications either during or after the procedure. Obtained biopsy specimens were fixed in 3% glutaraldehyde stabilized with 1M cacodylate buffer at pH 7.4, postfixed in 1% OsO4 on cacodylate buffer. The materials were then dehydrated and embedded in epon. The Irvin-Fischer test for statistical analysis was used. A p value < 0.05 was considered significant. The presence of focal mild loss of myofibrils (+) was statistically more frequent in the patients in A group (p < 0.05). It was found in 86% (6/7) of cases in A group, while in the B group was observed in 20% of (2/10) cases.(ABSTRACT TRUNCATED AT 250 WORDS)

[Cardiogenic shock. Coronary angioplasty after failed intravenous thrombolysis]

Rescue coronary angioplasty (PTCA) was employed as reperfusion strategy after unsuccessful intracoronary infusion of streptokinase in 13 patients with AMI complicated by cardiogenic shock (CS). Reperfusion defined as reestablishment of TIMI 3 degree flow in the infarct related artery and reduction in luminal narrowing to less than 50% was achieved in 8 patients (61.5%). The failure of PTCA was caused by: inability to cross occlusion in 2 patients and recurrent thrombosis despite repeated dilatations resulting in hemodynamic instability requiring cardiopulmonary resuscitations during the procedure in 3 patients. There was no significant differences in mean age, sex, time from onset of symptoms, LVEF, artery involved, extent of coronary disease and incidence of cardiopulmonary resuscitations during the procedures. There where 4 in-hospital deaths among patients with failed PTCA (80%) compared to 25% mortality in reperfused group. We conclude that PTCA is an effective method of achieving reperfusion in patients with CS complicating AMI after failed thrombolysis with intracoronary streptokinase and that it improves in-hospital survival.

[Acute myocardial infarction with shock. Intracoronary thrombolysis]

Of 932 pts with acute myocardial infarction (AMI) who underwent reperfusion therapy (RT) by intracoronary streptokinase (IC.STK), 32 pts had cardiogenic shock (CS). Shock was defined as systolic blood pressure (BP) < or = 80 mmHg without inotropic support or BP < or = 90 mmHg with inotropic or balloon counterpulsation support and left ventricular end diastolic pressure < 18 mmHg and clinical symptoms of hypoperfusion. Time from onset of symptoms to initiation of therapy was less than 6 hours. Reperfusion was defined as reestablishment of antegrade TIMI-2 or 3 flow in occluded artery. Comparison revealed no significant differences in sex, age, time after onset of symptoms, artery involved, history of previous AMI, left ventricular ejection fraction and in extent of coronary disease between pts with successful and failed thrombolysis. IC.STK was successful in 12 pts with CS (37.5%) and in 67.2% of pts without CS (p < or = 0.001). Mortality rate in pts with CS was 25% in reperfused and 81.8% among nonreperfused (p = 0.0095).

CONCLUSIONS

1. IC.STK gives a considerably lower rate of reperfusion in pts with AMI complicated by CS. 2. No influence on the frequency of effective reperfusion with respect to the analyzed clinical and angiographical data was found. 3. The high mortality in the group with unsuccessful reperfusion as well as the low effectiveness of the IC STK indicates the necessity to apply more effective methods of reperfusion in pts with AMI complicated by CS.

[Angioplasty of several stenoses including the left main coronary artery in a patient with acute circulatory insufficiency after myocardial infarction]

A 74 year old man with diabetes and multivessel coronary heart disease involving also left main coronary artery is presented. The patient was admitted to the hospital because of acute myocardial infarction. PTCA of left main coronary artery and other four severe stenoses was attempted. The clinical status after procedure, short-term (after eight months) and long-term (after five years) was much improved.

[Holter monitoring in diagnosis of syncope]

Thirty two patient with a history of brief unconsciousness underwent a constant ECG monitoring with Holter's technique for 24-72 hours. Syncope was noted in 16 patients. Cardiac arrhythmia was a cause of unconsciousness in 14 patients whereas no such a pathology was seen in the remaining two patients. No syncope was seen during ECG monitoring in 16 patients. Loss of consciousness was found in the majority of patients monitored for 72 hours. This technique may be valuable in the diagnosis of syncope, especially when it appears during ECG monitoring.

[Invasive treatment of recent myocardial infarction. Evaluation of left ventricular function]

Hemodynamic parameters of left ventricular function were assessed in 179 patients with acute myocardial infarction, who were treated with intracoronary thrombolysis during first six hours after the onset of chest pain. Some of them were subjected to coronary angioplasty. Patency of the infarct related artery was controlled between the 2nd and 3rd week after acute myocardial infarction concomitant with evaluation of EF and LVEDP. Reperfusion of the infarct related artery was obtained in 121 patients (67.6%) and also significant increase of EF was observed in those patients. EF rose in patients with a patent coronary artery after 2-3 weeks (not significant) in contrast to patients with obstructed coronary artery in whom there was a fall in EF. The rise of EF was more pronounced in patients with reperfusion reached in 3 hours after the onset of infarct pain and without coronary angioplasty. It was shown that LVEDP is not usefull in estimation of left ventricular function.

[Effect of beta adrenergic blocking drugs on the prognostic value of ST-segment depression during exercise electrocardiogram testing]

Exercise testing has been shown to be predictive for future cardiac events in patients with established diagnosis of coronary heart disease. Exercise test parameters associated with poor prognosis may be unreliable if patient is receiving beta adrenergic agents. The purpose of this study was: 1) to compare the results of exercise testing performed before and during beta blocking therapy, and 2) to determine the role of beta blockers in the prognostic significance of the ST-segment response recorded during exercise testing. The study population consisted of 518 patients (mean age 52 +/- 7 years) with coronary heart disease. The diagnosis was based on the presence of one of the following three criteria: 1) typical history and significant ST-segment depression on resting or exercise electrocardiogram, 2) history of myocardial infarction, 3) significant coronary angiographic abnormalities. In all patients symptom-limited exercise test was performed before and two weeks after the onset of beta blocker therapy. The data from the first and second tests were estimated for significance of differences between the mean values with following results: maximal heart rate--135 +/- 21 and 123 +/- 19 bpm (p less than 0.001), maximal work load achieved--98 +/- 43 and 109 +/- 44 W (p less than 0.001), maximal systolic blood pressure--171 +/- 28 and 163 +/- 26 mmHg (p less than 0.001). Occurrence of characteristic ST-segment depression was more frequent during the first than during the second test (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Proarrhythmic response to antiarrhythmic drug as a risk factor for sudden cardiac death in patients with ischemic heart disease

The prognostic significance of arrhythmogenic response to an antiarrhythmic drug was studied. In 782 patients with ischemic heart disease (IHD) and frequent and/or complex ventricular premature beats (VPBs), 1,041 drug tests guided by 24-hour Holter monitoring were conducted. The following drugs were assessed: beta blockers, disopyramide, mexiletine, amiodarone. Proarrhythmia was defined as: (1) greater than 4-fold increase in VPBs, (2) greater than 10-fold increase in repetitive forms, or (3) new occurrence of ventricular tachycardia or ventricular fibrillation (VT/VF). During a follow-up of 1-49 months (mean 22) patients were treated with antiarrhythmic drugs found to be safe in control Holter monitoring. Proarrhythmic effects were observed in 8.4% of patients. No drug was completely free of this type of reaction. In long-term observation, cardiac death and sudden death occurred in 53 and 32 patients, respectively. With actuarial analysis (Kaplan-Meier method, log-rank test) there was a significant difference in cardiac death (P less than 0.01) and sudden death rate (P less than 0.05) of proarrhythmia (+) compared with proarrhythmia (-) patients at 1 year (11% vs 4%, 7% vs 3%) and 3 years (24% vs 11%, 16% vs 7%). Proarrhythmic response was an independent risk factor apart from myocardial infarction, VT/VF, ejection fraction less than 40% and QTc greater than 440 msec. Arrhythmogenic response to antiarrhythmic drugs seems to be an additional predictor of sudden death in IHD.

[Scintigraphy of "hot foci" in myocardial infarction while using technetium 99m labelled pyrophosphate and antimyosin antibodies labelled with radioactive indium 111]

Comparison of the scintigraphic diagnosis of the myocardial infarction with two radioactive substances is presented. Pyrophosphate labelled with radioactive 99mTc and anti-myosins labelled with radioactive 111In were used for this purpose.

[Myocarditis and dilated cardiomyopathy in scintigraphic evaluation using gallium-citrate 67 and antimyosin antibodies radiolabelled with indium 111]

Scintigraphic techniques of myocarditis diagnosis are presented. 67Ga-citrate and anti-myosins labelled with 111In-isotope have been used. Results were compared with those of heart biopsy.

Predictors of ventricular tachycardia inducibility in programmed electrical stimulation and the effectiveness of serial drug testing: Polish multicenter study

In 100 patients with IHD and complex ventricular arrhythmias, programmed electrical stimulation was performed using up to three extrastimuli at sinus rhythm, and paced 100, 120 and 140 beats/min delivered from the RV apex, outflow tract or the LV with ventricular mapping to evaluate late potentials (LP) in 41 patients. Sustained monomorphic VT (SMVT) was provoked in 91% of 42 patients with a history of VT/VF, P less than 0.001, all five patients had SMVT in 24-hour ECG, P less than 0.005, and 91% of 21 patients with LV dyskinesis, P less than 0.01. After depolarizations were found in 62% of 21 patients with a history of VT, in 58% of 31 patients with inducible VT, P less than 0.01 and in five of six patients with LV dyskinesis. In patients with inducible VT, LP had a higher amplitude (105 +/- 35 vs 60 +/- 47 microV) and were more delayed (202 +/- 96 vs 133 +/- 75 msec) than in noninducible patients. In 17 patients, serial drug testing was performed after oral administration using mexilitene, disopyramide, chinidine, propafenone, sotalol, and amiodarone. If one drug was tested, the therapy efficacy was 25%, if two drugs-60%, and if three drugs-75%. In eight patients, VT was inducible in all tests, but in only one of these patients chronic antiarrhythmic therapy was not effective. We conclude that the most important predictors of VT inducibility are a history of VT or 24-hour ECG, and LV dyskinesis. Serial drug testing is efficient only when many drugs are tested, but even if VT is inducible, it does not exclude the possibility of a good clinical outcome in chronic therapy.

[A case of paroxysmal ventricular tachycardia surgically treated based on electrophysiological diagnosis]

There was presented a case of recurrent ventricular tachycardia in the patient after myocardial infarction. Considering uneffective pharmacotherapy and several cardiac arrests, the patient underwent guided endo-cardiotomy based on complex electrophysiological diagnostics (including intraoperative examination). Postoperative period was uncomplicated. There were no recurrences of ventricular tachycardia during 18-month follow-up.

[Late right and left ventricular potentials using inter-cardiac recording in patients with ischemic heart disease--methodologic and clinical problems]

The aim of the study was to compare detection frequency of late inter-cardiac potentials recorded from the right and left ventricle. There was also estimated relationship between their incidence and ventricular tachycardia or fibrillation occurrence. 41 patients with ischemic heart disease underwent the study. Electrophysiologic examination were performed because of ventricular tachycardia and/or fibrillation attacks or complex ventricular arrhythmias recorded in ECG Holter monitoring. In 11 patients intracardiac electrocardiograms were recorded from both ventricles, in 29 only from the right and in 1 from the left one. All patients underwent programmed right and/or left ventricular stimulation. Left ventricular end-diastolic diameter, segmental contractility and ejection fraction were echocardiographically estimated. Study results were statistically analyzed by means of CHI2 and t-Student tests for unpaired variables. Late potentials were more frequently observed in patients with left ventricular dyskinesis (p less than 0.01) and decreased ejection fraction. Late potentials recorded in patients with a history of ventricular tachycardia or fibrillation were more delayed to proceeded QRS complex and had a greater amplitude. This prolongation of ventricular activation can make an anatomic substrate for dangerous ventricular arrhythmias occurrence. Since the presence of late potentials in patients with contractility disorders is connected with more frequent incidence of spontaneous and provoked ventricular arrhythmias, endocardial late potentials recording may be of a prognostic value, if it is performed from both ventricles.

Atrial natriuretic peptide secretion in heart transplant patients

Plasma atrial natriuretic peptide (ANP), plasma renin activity (PRA), aldosterone (ALD) and vasopressin (VP) were assessed in six heart transplant patients (HTP) and ten healthy subjects under bed rest conditions and 60 and 120 minutes after head-out water immersion (WI). Bed rest had no significant influence on these parameters. WI raised plasma volume (PV) to the same extent in both groups. This increase of PV was accompanied by significant suppression of PRA, ALD and VP and an increase of plasma ANP. In HTP basal plasma ANP was significantly elevated and the ANP response to central hypervolemia reduced. Significantly elevated VP plasma levels were also found in HTP. These endocrine abnormalities in HTP seem to be caused by latent failure of the transplanted heart. No direct correlation was found between plasma ANP and PRA, ALD and VP under basal conditions and after WI in either HTP or normals.

Noninvasive quantification of jeopardized myocardial mass in dogs using 2-dimensional echocardiography and thallium-201 tomography

The evaluation of jeopardized myocardial mass is important in defining the effect of interventions during myocardial infarction. To quantitate the in vivo mass at risk, 2-dimensional echocardiography (2-D echo) and thallium-201 single-photon emission computed tomography (SPECT) was performed in 10 closed-chest dogs after circumflex coronary artery occlusion. The 2-D images were manually digitized to compute left ventricular (LV) mass using a modified Simpson's rule algorithm. This measure of LV mass correlated well with the actual LV mass (r = 0.97). Perfused myocardial mass was estimated from thallium SPECT images 4 hours after occlusion using a region-growing algorithm. After the dogs were killed, the jeopardized mass was outlined using a dual perfusion staining technique using triphenyltetrazolium chloride and Evans blue dye. The actual perfused mass was well estimated by the thallium images (r = 0.96). The noninvasively determined mass at risk was calculated as: 2-D mass--thallium SPECT mass, and correlated well with the pathologically determined mass at risk (r = 0.91). Thus, the jeopardized mass may be determined noninvasively by using 2-D echo and thallium-201 tomography. This approach may provide further information regarding the effect of intervention therapy on jeopardized myocardium.

Long-term intravenous infusion of antiarrhythmic drugs using a totally implanted drug delivery system

In vitro and in vivo testing was performed to establish the feasibility of a totally implantable pump system to deliver antiarrhythmic agents. In vitro flow characteristics suggested predictable day to day delivery with acceptably small variations in flow with changes in reservoir volume or temperature. During 3 months of in vitro testing, procainamide and bretylium were found suitable for long-term delivery. Delivery of lidocaine was limited by high viscosity and corrosion of steel elements within the pump. The pump was implanted in a subcutaneous pocket in four dogs. Procainamide (0.5 g/ml), delivered at 4 ml/day (70 mg/kg body weight per day), provided a mean steady state drug concentration of 5.3 micrograms/ml. Bretylium (50 mg/ml), delivered at 8 ml/day (13 mg/kg per day), provided a steady state concentration of 0.8 micrograms/ml (range 0.4 to 1.4). Long-term intravenous administration of therapeutic doses of bretylium and procainamide with this delivery system has been demonstrated in dogs and appears to be feasible in human subjects.

DNA synthesis in coronary collaterals after coronary artery occlusion in conscious dog

With [3H]thymidine, DNA synthetic activity in coronary collateral arterioles was assessed in dogs subjected to progressive stenosis of the left circumflex coronary artery for different periods (36 h-5 days). Coronary flow, reactive hyperemia, and pressure gradient (aortic pressure, peripheral coronary pressure) were measured. Normal animals and animals with sham operations served as controls. Labeling of nuclei was seen in seven of the constricted dogs. Proliferative activity was highest at the level of the smallest diameters of the collateral vessels (midzone). There was heavy labeling in intima and media. Adventitial and myocardial mesenchymal cells also incorporated [3H]thymidine. No radioactive DNA was found in control animals. The data suggest that the active growth process in collaterals after constriction of the left circumflex coronary artery appears early, as there is evidence of collateral growth after 36 h of constriction. Peak growth as evidenced by [3H]thymidine incorporation was reached when the occlusion period was 4 days.