The mitochondrial single-stranded DNA binding protein is essential for initiation of mtDNA replication

We report a role for the mitochondrial single-stranded DNA binding protein (mtSSB) in regulating mitochondrial DNA (mtDNA) replication initiation in mammalian mitochondria. Transcription from the light-strand promoter (LSP) is required both for gene expression and for generating the RNA primers needed for initiation of mtDNA synthesis. In the absence of mtSSB, transcription from LSP is strongly up-regulated, but no replication primers are formed. Using deep sequencing in a mouse knockout model and biochemical reconstitution experiments with pure proteins, we find that mtSSB is necessary to restrict transcription initiation to optimize RNA primer formation at both origins of mtDNA replication. Last, we show that human pathological versions of mtSSB causing severe mitochondrial disease cannot efficiently support primer formation and initiation of mtDNA replication.

Topoisomerase 3α Is Required for Decatenation and Segregation of Human mtDNA

How mtDNA replication is terminated and the newly formed genomes are separated remain unknown. We here demonstrate that the mitochondrial isoform of topoisomerase 3α (Top3α) fulfills this function, acting independently of its nuclear role as a component of the Holliday junction-resolving BLM-Top3α-RMI1-RMI2 (BTR) complex. Our data indicate that mtDNA replication termination occurs via a hemicatenane formed at the origin of H-strand replication and that Top3α is essential for resolving this structure. Decatenation is a prerequisite for separation of the segregating unit of mtDNA, the nucleoid, within the mitochondrial network. The importance of this process is highlighted in a patient with mitochondrial disease caused by biallelic pathogenic variants in TOP3A, characterized by muscle-restricted mtDNA deletions and chronic progressive external ophthalmoplegia (CPEO) plus syndrome. Our work establishes Top3α as an essential component of the mtDNA replication machinery and as the first component of the mtDNA separation machinery.

Nucleotide pools dictate the identity and frequency of ribonucleotide incorporation in mitochondrial DNA

Previous work has demonstrated the presence of ribonucleotides in human mitochondrial DNA (mtDNA) and in the present study we use a genome-wide approach to precisely map the location of these. We find that ribonucleotides are distributed evenly between the heavy- and light-strand of mtDNA. The relative levels of incorporated ribonucleotides reflect that DNA polymerase γ discriminates the four ribonucleotides differentially during DNA synthesis. The observed pattern is also dependent on the mitochondrial deoxyribonucleotide (dNTP) pools and disease-causing mutations that change these pools alter both the absolute and relative levels of incorporated ribonucleotides. Our analyses strongly suggest that DNA polymerase γ-dependent incorporation is the main source of ribonucleotides in mtDNA and argues against the existence of a mitochondrial ribonucleotide excision repair pathway in human cells. Furthermore, we clearly demonstrate that when dNTP pools are limiting, ribonucleotides serve as a source of building blocks to maintain DNA replication. Increased levels of embedded ribonucleotides in patient cells with disturbed nucleotide pools may contribute to a pathogenic mechanism that affects mtDNA stability and impair new rounds of mtDNA replication.

Human mitochondria contain a small double-stranded DNA genome (mtDNA) of only 16,569 base pairs (bp) that encodes 13 essential subunits of the oxidative phosphorylation system. Depletion of mtDNA and different types of mtDNA mutations cause mitochondrial disease, and are also implicated in biological ageing. For almost half a century it has been known that mtDNA contains ribonucleotides, but their identity and precise location are not known. The source of these ribonucleotides and their relevance for mitochondrial genome stability in healthy individuals and in patients with mitochondrial defects has not been addressed. We have used a combination of next-generation sequencing, and in vivo and in vitro biochemistry to address some of these questions. Our findings demonstrate that DNA polymerase γ-dependent incorporation is the main source of ribonucleotides in mtDNA and argues against the existence of ribonucleotide excision repair pathways in human mitochondria. Our data also reveal that when dNTP pools are limiting, ribonucleotides serves as a second line of building blocks for DNA synthesis. We also demonstrate increased levels of embedded ribonucleotides in patient cells with disturbed nucleotide pools, which may constitute a new pathogenic mechanism that affects mtDNA stability and impairs later rounds of mtDNA replication.

An Adaptable High-Throughput Technology Enabling the Identification of Specific Transcription Modulators

Mitochondria harbor the oxidative phosphorylation (OXPHOS) system, which under aerobic conditions produces the bulk of cellular adenosine triphosphate (ATP). The mitochondrial genome encodes key components of the OXPHOS system, and it is transcribed by the mitochondrial RNA polymerase, POLRMT. The levels of mitochondrial transcription correlate with the respiratory activity of the cell. Therefore, compounds that can increase or decrease mitochondrial gene transcription may be useful for fine-tuning metabolism and could be used to treat metabolic diseases or certain forms of cancer. We here report the establishment of a novel high-throughput assay technology that has allowed us to screen a library of 430,000 diverse compounds for effects on mitochondrial transcription in vitro. Following secondary screens facilitated by the same assay principle, we identified 55 compounds that efficiently and selectively inhibit mitochondrial transcription and that are active also in cell culture. Our method is easily adaptable to other RNA or DNA polymerases and varying spectroscopic detection technologies.

Abstract 222: Inhibitors of mitochondrial transcription (IMT) specifically affect cancer cell proliferation

Mitochondria contain a unique DNA genome (mtDNA) that encodes a number of key components of the respiratory chain. Levels of mtDNA gene expression correlate with the metabolic requirements of mammalian cells. Recently, the role of mitochondrial function for the development and progression of cancer has been highlighted. Oncogenes have been identified to redirect mitochondrial functions to increase cancer cell survival. Increased levels of oxidative phosphorylation have also been implicated in cancer cell resistance towards drugs. In agreement with this notion, compounds that inhibit respiration may specifically target such resistant cells. Finally, it was demonstrated that inhibition of mitochondrial gene expression leads to apoptosis in rapidly dividing cells. Based on these observations, we present a completely novel principle different from known electron transfer chain blockers to treat cancer by inhibiting mtDNA transcription. To this end a study to identify and characterize inhibitors of mitochondrial transcription (IMTs) with lead-like properties was initiated. A high throughput biochemical screening campaign was performed identifying small molecular weight inhibitors of PolRMT, the mitochondrial RNA polymerase, which controls mtDNA transcription. Upon hit optimization, potent compounds with biochemical and cellular IC50s in the low nanomolar range have been identified. IMTs displayed good physicochemical and pharmacological properties. They have been shown to be inactive on other RNA polymerases proving their excellent specificity. Testing IMTs in assays for cancer cell proliferation revealed potent inhibition of sensitive cell lines (double digit nanomolar range). Interestingly, none of the tested primary non-cancer cell lines was affected by the IMTs, indicating a good therapeutic window. Testing selected IMTs in pharmacokinetic studies in vivo revealed high exposures and no detectable adverse effects (single and repeated dosing). Medicinal chemistry optimization will help to identify candidate compounds for efficacy testing in xenograft models.

Citation Format: Tim Bergbrede, Axel Choidas, Raffaela Di Lucrezia, Sascha Menninger, Anke Unger, Koch Uwe, Peter Nussbaumer, Nina Bonekamp, Emily Hoberg, Victor Posse, Andrea Felser, Maria Falkenberg, Nils Göran Larsson, Claes M. Gustafsson, Bert M. Klebl. Inhibitors of mitochondrial transcription (IMT) specifically affect cancer cell proliferation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 222.

[Vocational inpatient and post-treatment proposals in cardiac rehabilitation patients (BERUNA): results of a randomized controlled trial]

BACKGROUND

The “Verband Deutscher Rentenversicherungsträger (VDR)” required the intense focus on vocational rehabilitation of medical problems since the early 1990s. By integrating elements of the working environment in the structures and processes of medical rehabilitation, vocational problems can be identified early in order to take appropriate countermeasures. Posttreatment proposals off er a way to provide a reliable long-term success.

OBJECTIVE

The intention of this study is the implementation and the investigation of effectiveness of an intensified vocational program that integrates besides the in-patient rehabilitation post-treatment proposals as well.

METHODS

Cardiac rehabilitation patient occurring special vocational problems participe. The recruited patients were randomized to either the vocational program or the common cardiac rehabilitation.Primary outcome was the vocational reintegration 12 months after the end of rehabilitation.The database was collected through a query of the pension insurance accounts and questionnaires.

RESULTS

306 people were included to the study at the beginning of rehabilitation. Rates of response:95 % of the survey to the end of rehabilitation,77 % of the survey 6 months and 73 % of the survey 12 months after the end of rehabilitation.The sample was characterized by great interferences of their professional involvement and a high demand for vocational treatments. At the beginning of the rehabilitation 50 % of study participants intended to make an application for reduction-pension. Nevertheless, one year after the end of rehabilitation a surprisingly high rate of vocational reintegration by over 70 % in both groups (IG: 72 %, KG: 75 %, p < 0.929) was indicated.The majority of the unemployed patients at the beginning of rehabilitation remained in the unemployment (IG: 69 %, KG: 65 %, p < 0.757). The participation rate at the post-treatment proposals was 42%.

CONCLUSION

The results show that vocational programs in rehabilitation need to be revised, including with regard to the question, whether and in what way post-treatment proposals must be changed.

The amino terminal extension of mammalian mitochondrial RNA polymerase ensures promoter specific transcription initiation

Mammalian mitochondrial transcription is executed by a single subunit mitochondrial RNA polymerase (Polrmt) and its two accessory factors, mitochondrial transcription factors A and B2 (Tfam and Tfb2m). Polrmt is structurally related to single-subunit phage RNA polymerases, but it also contains a unique N-terminal extension (NTE) of unknown function. We here demonstrate that the NTE functions together with Tfam to ensure promoter-specific transcription. When the NTE is deleted, Polrmt can initiate transcription in the absence of Tfam, both from promoters and non-specific DNA sequences. Additionally, when in presence of Tfam and a mitochondrial promoter, the NTE-deleted mutant has an even higher transcription activity than wild-type polymerase, indicating that the NTE functions as an inhibitory domain. Our studies lead to a model according to which Tfam specifically recruits wild-type Polrmt to promoter sequences, relieving the inhibitory effect of the NTE, as a first step in transcription initiation. In the second step, Tfb2m is recruited into the complex and transcription is initiated.

Pharmacological activities of Vitex agnus-castus extracts in vitro

The pharmacological effects of ethanolic Vitex agnus-castus fruit-extracts (especially Ze 440) and various extract fractions of different polarities were evaluated both by radioligand binding studies and by superfusion experiments. A relative potent binding inhibition was observed for dopamine D2 and opioid (micro and kappa subtype) receptors with IC50 values of the native extract between 20 and 70 mg/mL. Binding, neither to the histamine H1, benzodiazepine and OFQ receptor, nor to the binding-site of the serotonin (5-HT) transporter, was significantly inhibited. The lipophilic fractions contained the diterpenes rotun-difuran and 6beta,7beta-diacetoxy-13-hydroxy-labda-8,14-dien . They exhibited inhibitory actions on dopamine D2 receptor binding. While binding inhibition to mu and kappa opioid receptors was most pronounced in lipophilic fractions, binding to delta opioid receptors was inhibited mainly by a aqueous fraction. Standardised Ze 440 extracts of different batches were of constant pharmacological quality according to their potential to inhibit the binding to D2 receptors. In superfusion experiments, the aqueous fraction of a methanolic extract inhibited the release of acetylcholine in a concentration-dependent manner. In addition, the potent D2 receptor antagonist spiperone antagonised the effect of the extract suggesting a dopaminergic action mediated by D2 receptor activation. Our results indicate a dopaminergic effect of Vitex agnus-castus extracts and suggest additional pharmacological actions via opioid receptors.

Quantitative high performance liquid chromatographic analysis of diterpenoids in agni-casti fructus

Pharmacological data have indicated that part of the dopaminergic activity of Vitex agnus-castus is attributed to the labdan diterpenoids found in the fruits. Therefore an analytical method for the standardization of rotundifuran (1), vitexilactone (2) and 6 beta,7 beta-diacetoxy-13-hydroxy-labda-8,14-diene (3) was developed. Because of the time-consuming and expensive isolation of the diterpenoids, p-cymene was chosen as an internal standard. The concentration of rotundifuran in different extracts and trade samples of the drug varies between 0.04 and 0.30% in the drug and between 1.04 and 2.23% in the extract. The concentration of vitexilactone was generally lower between 0.016 and 0.167% for the drug and between 0.34 and 1.01% for the extract. The determined concentration of 6 beta,7 beta-diacetoxy-13-hydroxy-labda-8,14-diene in the drug was in the range of 0.02 and 0.10% and in the extract in the range of 0.18 and 0.80%. Determination of the factors of correction of p-cymene gave 5.63 for rotundifuran, 2.73 for vitexilactone and 3.74 for 6 beta,7 beta-diacetoxy-13-hydroxy-labda-8,14-diene.

Comparison of two sample preparation techniques for sniffing experiments with broccoli (Brassica oleracea var. italica Plenck)

The suitability of the headspace solid phase microextraction (HSSPME) for gas chromatography-olfactometry (GC-O) with aroma extract dilution analysis in comparison to the dynamic head space sampling on a Tenax trap was tested exemplarily by the aroma volatiles of fresh broccoli. A high number of odour sensations in qualitative olfactometry was registered with both sample preparation techniques. The key aroma compounds of the fresh broccoli material are represented by high flavour dilution factors with dynamic head space sampling and headspace SPME. The SPME method has found to be a convenient and fast technique suitable especially for qualitative GC-O. The adsorption selectivity of the fiber and the substance discrimination have to be taken into account for quantitative use like aroma extract dilution analysis.

[Psychological comorbidity in patients with alarming chest pain symptoms]

About 1/3 of patients with chest pain undergoing coronary arteriography (CA) have no coronary artery disease (CAD). Individuals with non-CAD chest pain may be younger and more likely to be female; they may express higher degrees of neuroticism. Are those features stable enough to justifi; exclusion from CA if present? To investigate this issue, data on psychodiagnostic parameters (depression, anxiety, somatic complaints) were obtained in patients before this were referred to CA. Inclusion criteria were a chief complaint of chest pain with episodes of angina-like pain at rest, suspicious enough to warrant cardiac catherisation; and no prior history of CAD or other organic heart disease. The sample consisted of 77 patients, recruited from 89 eligible patients. 12 patients were excluded because CA findings were missing for multiple reasons. CA was conducted by Judkins technique. Patients were labeled as CAD (-) if no stenosis were detectable. In 50 (65%) of cases CA findings were positive and in 27 (35%) findings were negative. CAD+ were significantly older (p < 0.05); the superiority in both groups were male. Prevalence of emotional disorders was markedly more pronounced in both groups in comparison to the normal population and to a group of male myocardial infarction survivors. However, those features did not discriminate between the groups. Long acting chest pain was predictive for high degrees of emotional disability (relative risk 5.33; 95% Kl 1.6-61.6; p < 0.012). Chest pain at rest is a major source of anxiety, depression and subsequent somatic preoccupation despite its ischaemic or functional origin. It leads to clinically relevant adjustment disorders in a significant proportion of chest pain patients and triggers emotional disstress. These factors may thus have less impact on risk stratification than expected.

[Calcium antagonists and prevention of post-angioplasty restenosis]

Five randomised double blind clinical trials have assessed the effects of long term therapy with calcium antagonists on post-coronary angioplasty restenosis. Nifedipine 40 mg/day was tested in 241 patients by Whitworth et al: there was no difference in the incidence of restenosis between the treatment and placebo groups. Corcos et al studied the effects of diltiazem 270 mg/day in 92 patients: there was no significant difference between the two groups. In a study of 201 patients, O'Keefe et al found no significant difference in incidence of restenosis in a group treated with diltiazem (240 to 360 mg/day) compared with placebo. The fourth trial, conducted by Unverdorben et al, not yet fully published, in 170 patients, showed a significant reduction in restenosis in patients treated with diltiazem 180 mg/day (p = 0.03). Finally, the VAS trial (Verapamil Angioplasty Study) showed high dose verapamil (480 mg/day) to reduce the incidence of restenosis in a subgroup of patients with stable angina and high risk of restenosis.

The effects of calcium antagonists after PTCA

Experiments have shown that calcium antagonists can prevent restenosis after coronary angioplasty. The first controlled clinical trials, however, failed to show such a benefit after PCTA: the recurrence rate was not significantly influenced by either nifedipine (10 mg q.i.d.) or diltiazem (90 mg t.i.d.). Another trial used a higher dose of diltiazem (mean 329 mg per day) in a larger number of patients, but again the result was negative. In contrast, diltiazem 180 mg per day was reported more recently to significantly reduce restenosis, and high-dose verapamil treatment was similarly successful in a subgroup of patients with stable angina pectoris at the time of primary successful PCTA. Despite some important limitations of the five monocentre trials, the combined analysis of the results shows that calcium antagonists have a beneficial effect on restenosis rate after PTCA. Whether this effect is limited to heart rate slowing substances and to special subgroups of lesions has to be clarified by further studies in sufficiently large patient populations.

Verapamil treatment after coronary angioplasty in patients at high risk of recurrent stenosis

OBJECTIVE

To evaluate the efficacy of high-dose verapamil treatment (240 mg twice daily) in the prevention of angiographic restenosis after primary successful coronary angioplasty in patients at high risk of recurrent obstruction.

DESIGN

A placebo controlled, double blind trial in which patients with stable angina pectoris and patients with unstable angina or non-Q wave infarction treated with 330 mg aspirin and 75 mg dipyridamole twice daily were randomised to a verapamil group or a control group. Follow up angiography was performed 6 months after angioplasty or sooner if signs of recurrent ischaemia developed.

SETTING

University department of cardiology.

PATIENTS

196 consecutive patients undergoing coronary angioplasty from the beginning of April 1987 to the end of March 1989 and meeting the selection criteria that included the presence of at least one of six predefined risk factors for restenosis. At the time of coronary angioplasty 113 patients had unstable angina or non-Q wave infarction and 83 had stable angina pectoris.

RESULTS

In 89 (91%) patients in the verapamil group and in 83 (85%) control patients follow up angiograms were available. The restenosis rate was lower in the verapamil group (48.3%) than in the placebo group (62.7%) (odds ratio 0.56, 95% confidence interval (CI) 0.303 to 1.025 p = 0.059). Of the 172 patients in whom follow up angiograms were available, 24 (13 taking verapamil and 11 taking placebo) did not comply with the trial for more than 40 (34) days (mean (1 SD)). For the remaining 148 patients the restenosis rate was 47.4% in the verapamil group and 63.9% in the placebo group (odds ratio 0.52, 95% CI 0.271 to 0.993, p = 0.046). In the 97 patients with unstable angina or non-Q wave infarction the restenosis rate was not significantly influenced by verapamil (55.8% with verapamil v 62.2% with placebo, odds ratio 0.77, 95% CI 0.339 to 1.728, p = 0.520). In the 75 patients with stable angina pectoris the restenosis rate dropped from 63.2% with placebo to 37.8% with verapamil (odds ratio 0.36, 95% CI 0.137 to 0.917, p = 0.038).

CONCLUSION

The observed beneficial effect of high-dose verapamil treatment on the angiographic restenosis rate in patients with stable angina pectoris and at increased risk of recurrent obstruction requires confirmation in further prospective studies.

Regular physical exercise and low-fat diet. Effects on progression of coronary artery disease

BACKGROUND

Significant regression of coronary and femoral atherosclerotic lesions has been documented by angiographic studies using aggressive lipid-lowering treatment. This study tested the applicability and effects of intensive physical exercise and low-fat diet on coronary morphology and myocardial perfusion in nonselected patients with stable angina pectoris.

METHODS AND RESULTS

Patients were recruited after routine coronary angiography for stable angina pectoris; they were randomized to an intervention group (n = 56) and a control group on "usual care" (n = 57). Treatment comprised intensive physical exercise in group training sessions (minimum, 2 hr/wk), daily home exercise periods (20 min/d), and low-fat, low-cholesterol diet (American Heart Association recommendation, phase 3). No lipid-lowering agents were prescribed. After 12 months of participation, repeat coronary angiography was performed; relative and minimal diameter reductions of coronary lesions were measured by digital image processing. Change in myocardial perfusion was assessed by 201Tl scintigraphy. In patients participating in the intervention group, body weight decreased by 5% (p less than 0.001), total cholesterol by 10% (p less than 0.001), and triglycerides by 24% (p less than 0.001); high density lipoproteins increased by 3% (p = NS). Physical work capacity improved by 23% (p less than 0.0001), and myocardial oxygen consumption, as estimated from maximal rate-pressure product, by 10% (p less than 0.05). Stress-induced myocardial ischemia decreased concurrently, indicating improvement of myocardial perfusion. Based on minimal lesion diameter, progression of coronary lesions was noted in nine patients (23%), no change in 18 patients (45%), and regression in 13 patients (32%). In the control group, metabolic and hemodynamic variables remained essentially unchanged, whereas progression of coronary lesions was noted in 25 patients (48%), no change in 18 patients (35%), and regression in nine patients (17%). These changes were significantly different from the intervention group (p less than 0.05).

CONCLUSIONS

In patients participating in regular physical exercise and low-fat diet, coronary artery disease progresses at a slower pace compared with a control group on usual care.

[Therapeutic possibilities, respective implications in silent ischemia]

In principle, all forms of treatment applied in patients with symptomatic coronary heart disease may likewise be used in silent myocardial ischemia. Based on Bayes' theorem, therapeutic measures may only be applied in patients with a positive exercise ECG with a high likelihood of coronary heart disease, and/or with myocardial ischemia revealed by another, ECG-independent method, such as, for example, thallium-scintigraphy. As symptomatic improvement cannot be expected in patients with silent myocardial ischemia, therapeutic efficacy can only be documented by an improvement in prognosis. Results of controlled randomized trials are not available in silent myocardial ischemia; therapeutic recommendations can, therefore, only be based on analogous results obtained in patients with symptomatic forms of the disease. Apart from reduction of the known risk factors of coronary heart disease, aspirin may be given to all patients at risk. Among the antiischemic antianginal drugs, beta-receptor blocking agents without intrinsic-sympathomimetic activity may be expected to improve prognosis. In asymptomatic patients with left-stem stenosis and three-vessel disease with impaired left-ventricular function (also, in two-vessel disease with a stenotic dominant LAD) aorto-coronary bypass surgery may be considered in order to improve prognosis.

Increased plasma viscosity and erythrocyte aggregation: indicators of an unfavourable clinical outcome in patients with unstable angina pectoris

OBJECTIVE

To determine the prognostic significance of altered plasma viscosity and erythrocyte aggregation in unstable angina.

DESIGN

A prospective study of 96 consecutive patients with unstable angina allocated to one of two groups according to predefined threshold values for plasma viscosity and erythrocyte aggregation at study entry. The patients received a standardised treatment and were followed up for six months or until angioplasty or bypass surgery.

MAIN OUTCOME MEASURE

Frequency of myocardial infarction.

RESULTS

Myocardial infarctions occurred in 7/26 patients with a plasma viscosity greater than or equal to 1.38 mPa s and in 8/35 with a rate constant of erythrocyte aggregate formation greater than or equal to 0.5 mPa (corrected for plasma viscosity) but in only 4/70 with a plasma viscosity less than 1.38 mPa s and in 3/61 with an erythrocyte aggregation less than 0.5 mPa (odds ratios: 6.1 (95% confidence interval 1.3 to 31), p = 0.008, and 5.7 (95% CI 1.2 to 35), p = 0.016). Plasma viscosity and erythrocyte aggregation were more predictive of myocardial infarction than age, male gender, fibrinogen concentration, ST segment abnormalities, or coronary score. Furthermore, Holter monitoring with ST segment analysis showed that ischaemic episodes were more common in patients in whom the rate constant of erythrocyte aggregate formation was greater than 0.5 mPa (15/27 v 17/50, p = 0.029). Cardiac troponin T release was increased in patients with a plasma viscosity of greater than 1.38 mPa s (10/26 v 9/70, p = 0.010).

CONCLUSIONS

In patients with unstable angina a considerable increase in plasma viscosity and erythrocyte aggregation identified a subgroup of patients at a high risk of acute myocardial infarction in whom medical treatment was likely to be unsuccessful.

Calcium-antagonists in preventing restenosis following coronary angioplasty

In experimental studies the growth factor dependent proliferation and migration of medical smooth muscle cells was found to be inhibited by calcium-antagonists. Since this process seems to play an important role in the pathogenesis of recurrent stenosis, clinical trials were performed to evaluate the influence of calcium-channel blockers on restenosis rate after initially successful coronary angioplasty. However, according to the first 3 completed studies the restenosis rate was not decreased significantly either by the treatment with nifedipine or by the treatment with different dosages of diltiazem. The influence of high-dose verapamil treatment (Isoptin RR, 240 mg verapamil, twice daily) on the recurrence of coronary obstruction has been investigated by a recently completed prospective double-blind, placebo-controlled trial (VAS) which included 196 consecutive patients with at least one risk factor for restenosis. Patients with stable angina pectoris (n 75) and patients with unstable angina/non Q-wave infarction (n 97) were randomized separately. Follow-up angiography within 6 months after the procedure was performed in 88% of the recruited patients. Another 22 patients (11%) stopped the study medication before control angiography. At present, detailed data of the intention-to-treat analysis and the as-treated analysis of the results of VAS were submitted for publication.

[The noninvasive diagnosis of coronary heart disease in women. The exercise ECG or ST-segment analysis in the long-term ECG?]

The diagnostic value of an exercise ECG in women with the clinical symptoms of stable angina is limited because of its low accuracy in demonstrating coronary heart disease. A study of ambulatory patients was undertaken, involving 143 men and 29 women (mean age 55 [37-70] years), to determine whether ST-segment analysis of the 24-hour ECG gives better results, the coronary arteriogram providing the standard of comparison. 24-hour monitoring and the exercise ECG gave similar diagnostic results (66% vs 67%) in the 143 men. But in the 29 women 24-hour monitoring was diagnostically superior to the exercise ECG (76% vs 45%; P less than 0.01), as a result of a significantly higher specificity (64% vs 29%; P less than 0.05) and a tendency towards higher sensitivity (87% vs 60%; P = 0.13). As expected, the accuracy of the exercise ECG was thus lower in women than in men (P less than 0.05). There were no significant gender-specific differences for accuracy of 24-hour monitoring (76% in women, 66% in men; P less than 0.15). These data indicate that in women ST-segment analysis of the 24-hour ECG is better than the exercise ECG for demonstrating coronary heart disease.

Diagnostic value of ambulatory Holter monitoring for the detection of coronary artery disease in patients with variable threshold angina pectoris

Patients with chronic stable angina pectoris may present with either fixed or variable threshold symptoms. To evaluate the diagnostic value of ambulatory Holter monitoring for the detection of coronary artery disease (CAD) in patients with variable threshold angina, 216 consecutive candidates for coronary angiography were investigated prospectively. For comparison, a group of 55 consecutive patients with fixed threshold angina was studied under the same conditions. Patients with prior myocardial infarction or angiographically documented CAD were excluded. Within 4 months of Holter monitoring, the advised coronary angiography was performed in 77% of the patients with variable threshold angina and in 89% of the patients with fixed threshold angina (p less than 0.05). The prevalence of CAD was markedly lower in patients with variable threshold angina compared to patients with fixed threshold angina (54 vs 90%, p less than 0.001). CAD patients of both subgroups, however, did not differ significantly with respect to the number of obstructed vessels, the Gensini coronary score, the number with impaired left ventricular function (ejection fraction less than 50%) or the duration of ischemic episodes during Holter monitoring. Diagnostic accuracy of Holter monitoring did not differ between variable and fixed threshold angina groups (67 vs 78%). In 91% of the patients results obtained by Holter monitoring could be compared to the results of a bicycle stress test. In patients with fixed threshold angina the diagnostic accuracy was similar for both tests (80 vs 80%). In patients with variable threshold angina, the diagnostic accuracy of Holter monitoring exceeded that of the exercise stress test (68 vs 55%, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

[Perioperative myocardial ischemia in patients with peripheral arterial occlusive diseases]

Patients with peripheral vascular disease (PVD) often have coronary artery disease (CAD) which means an increased risk during anesthesia. The prevalence of CAD is nearly 50% among such patients. Owing to claudication, diagnostic stress tests can rarely be performed in PVD patients. In order to evaluate the frequency of transient perioperative myocardial ischemia, Holter monitoring was performed in 30 consecutive PVD patients with ASA II-III and AVK scale (Fontaine) II-IV who were undergoing femoropopliteal bypass surgery. Patients who had left bundle branch block and left ventricular hypertrophy or were taking digitalis medication were excluded from Holter monitoring. The ST-segment analysis of the frequency modulated recordings (n = 19) revealed episodes of myocardial ischemia in 26% of the patients. Most (75%) of the episodes occurred preoperatively, and 25%, during or after the anesthesia or during preparation for it. Risk factors for CAD were more often found in patients with ST segment alterations than in patients without ST segment deviations, even though the preoperative antianginal medication administered was comparable in the two subgroups. It is concluded that in a considerable subset of PVD patients silent myocardial ischemia occurs, which can be related to the different perioperative intervals by means of ST segment analyses of Holter recordings. The ST segment may allow a better insight into the cardiac state of PVD patients. Further studies are necessary in larger populations to test our suspicion.

Silent myocardial ischemia as a potential link between lack of premonitoring symptoms and increased risk of cardiac arrest during physical stress

The risk of cardiac arrest is increased during strenuous physical exercise in patients with stable coronary artery disease (CAD). Because premonitoring symptoms are rarely observed, silent myocardial ischemia may represent the pathophysiological basis for the induction of malignant ventricular arrhythmias. Holter monitoring was, therefore, performed in 40 consecutive patients entering a randomized intervention trial on progression of CAD. In 20 of 21 participants (95%) in the intervention program greater than or equal to 1 episode of silent myocardial ischemia was observed during the initial training session. The mean duration of silent myocardial ischemia per patient was 25 +/- 13 min/hr of training session. During normal daily activity only 5 patients (24%) experienced greater than or equal to 1 episode of silent myocardial ischemia (p less than 0.001) yielding a mean duration of 0.6 +/- 1.3 minutes of silent myocardial ischemia/hr of ordinary activity per patient (p less than 0.001 vs training session). During a control period of 24 hours without exercise training the incidence (33%) and mean duration of silent myocardial ischemia (0.8 +/- 2.1 min/hr/patient) were similar to those during normal daily activity on the day of the training session. During the training session the occurrence of frequent or repetitive ventricular arrhythmias was related to 10 silent myocardial ischemia episodes detected in 5 patients. During normal daily activity in 1 patient only was the onset of malignant ventricular arrhythmias associated with silent myocardial ischemia (p less than 0.05). Conditions and results of the Holter studies in the control group patients were comparable to those of the patients in the intervention group on the day without physical exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

[Validation of trend-supported ST segment analysis of long-term ECG recordings]

Trend recordings of relative ST-segment deviations represent a useful tool for the identification of ischemia-like episodes during Holter monitoring. For the generation of trend recordings beat-to-beat data are filtered. The influence of the time constant of the filter on the sensitivity and the specificity for the detection of ischemia-like ECG changes is unknown, however. Ischemia-like episodes were, therefore, simulated and recorded by a frequency modulated Holter recorder and by a conventional six-channel ECG system. Relative ST-segment deviations were filtered using a time constant of 8, 16, 32 or 64 s, or an arithmetic averaging over 9 s for the generation of ST-segment trends. The magnitude of short-lasting ST-segment deviations was underestimated, when beat-to-beat data were filtered using time constants of greater than or equal to 32 s. The influence of posture-related ECG changes on the ST-segment trends was investigated by recording lead CM5 in 14 consecutive patients in different positions by a conventional ECG system. Four out of the 14 patients developed ST-segment elevations greater than or equal to 0.1 mV during leftsided position. Only in these four patients were ST-segment deviations of similar magnitude recorded during the following Holter monitoring. The posture-related ST-segment changes were characterized by an abrupt onset and an abrupt end, resulting in a box-like shape which enabled their correct identification in the ST-segment trend analysis. In order to determine the relative frequency of posture-related ST-segment changes, 35 patients with coronary artery disease (CAD) and 35 patients without underwent Holter monitoring.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal antibodies specific for human cardiac myosin: selection, characterization and experimental myocardial infarct imaging

Radiolabelled anti-myosin antibodies (AM Ab) specifically accumulate in necrotizing myocytes and, therefore, allow the scintigraphic detection of myocardial infarction. In order to provide a constant supply of myosin-specific antibodies, the somatic cell fusion technique was used for the selection and propagation of AM Ab. Out of 126 antibody producing cell lines, nine were selected for further subcloning, due to their high affinity for purified myosin. For the in vivo imaging, two IgG-antibody molecules appeared particularly useful based on their antigenic specificity as assessed by immunoblotting and indirect immunofluorescence technique. After radiolabelling with iodine-123, undigested antibody molecules or their Fab fragments were injected into 10 dogs with experimental myocardial infarction. The accumulation of radioactivity in myocardial infarction was assessed by in vivo imaging and in vitro scintigraphy of ventricular slices stained by tetrazolium. The use of undigested AM Ab resulted in a high uptake ratio of radioactivity in the infarcted as compared to normal myocardium (20:1). In vivo infarct imaging, however, was not possible due to sustained labelling of the blood pool. The uptake ratio of iodine-123 labelled Fab fragments was only 9:1, but due to a faster plasma clearance of the Fab fragments, uptake in the heart could be visualized 5 h after intravenous injection. Clear differentiation between infarcted and noninfarcted myocardium, however, was limited by accumulation of radioactivity in the thoracotomy wound, in the liver, and in the stomach.

Circulating cardiac myosin light chains in patients with angina at rest: identification of a high risk subgroup

To detect myocardial cell damage, serum samples of 42 consecutive patients with angina at rest were screened for cardiac myosin light chains, which were detected in 22 patients (52%). In 17 of these patients there was a persistent release of myosin light chains lasting until the 4th hospital day, whereas in 7 patients myosin light chains were only detectable during the initial 24 h after admission. The presence of myosin light chains correlated with signs of ischemia in the electrocardiogram (ECG) (p less than 0.05) and with the extent of coronary artery narrowing (p less than 0.05). Cardiac myosin light chains were elevated in serum only if there was a greater than or equal to 75% diameter narrowing in at least one major vessel. In all five patients who developed transmural myocardial infarction during the course of their hospital stay, myosin light chains were detectable greater than or equal to 28 h before the diagnosis of myocardial infarction could be established by ECG criteria and conventional serum enzymes. Thus the detection of circulating cardiac myosin light chains enables one to identify a subgroup of patients with angina at rest having more severe coronary artery disease with a worse outcome.

[Balloon dilatation in unstable angina pectoris and acute myocardial infarct]

Early results after percutaneous transluminal coronary angioplasty (PTCA) in patients with unstable angina or acute myocardial infarction were compared with those in patients with stable angina. The primary success rate in 115 patients with unstable angina was 72%, in 73 with acute myocardial infarction 78%, and in 213 with stable angina 79%, i.e. there was no difference between the three groups. In patients with acute myocardial infarction and primary successful PTCA control angiography was performed one month after PTCA, in patients with unstable and stable angina 6 months after PTCA. Angiographic findings were identical in the three groups. But the results after successful balloon dilatation were dependent on the extent of primary success: in all three groups, patients in whom the post-dilatation control angiography revealed recurrence of stenosis the primary results were worse than in those without. There was no difference between those patients with lasting success and those with recurrence as regards cholesterol level, arterial hypertension, diabetes, and smoking habits. It is concluded that in every patient with acute symptoms of coronary heart disease the indication for PTCA should be considered.

Holter monitoring before, during and after percutaneous transluminal coronary angioplasty for evaluation of high-resolution trend recordings of leads CM5 and CC5 for ST-segment analysis

Frequency-modulated Holter monitoring of leads CM5 and CC5 was performed before, during and after percutaneous transluminal coronary angioplasty (PTCA) in 16 patients with stenosis of the left anterior descending coronary artery, in 5 patients with stenosis of the left circumflex coronary artery, and in 5 patients with stenosis of the right coronary artery. All patients presented with 1-vessel coronary artery disease and stable or unstable angina pectoris. ST-segment analysis was based on high-resolution trend recordings. During balloon inflations all patients had significant (at least 0.1 mV) ST-segment changes in lead CM5. In lead CC5, associated ST-segment deviations were found in 22 of 26 patients. During 29.2 +/- 13.6 hours before PTCA, 90 spontaneous episodes with significant ST-segment deviations were detected in 10 patients. Of these episodes, 17% were characterized by ST-segment deviations in lead CC5 only, 57% by ST-segment deviations in lead CM5 only, and 27% by simultaneous ST-segment deviations in both leads. Asymptomatic episodes occurred twice as frequently as symptomatic episodes (66 vs 34%). Symptomatic episodes were more often characterized by ST-segment deviations of at least 0.15 mV (48 vs 9%, p less than 0.001) and by ST-segment deviations observed in both leads simultaneously (48 vs 15%, p less than 0.001). During 34.8 +/- 10.6 hours after successful PTCA, 5 spontaneous asymptomatic episodes with significant ST-segment deviations were detected in 2 patients.

Myoglobin, creatine kinase-B isoenzyme, and myosin light chain release in patients with unstable angina pectoris

In 27 patients presenting with angina pectoris at rest and normal serum creatine kinase (CK) activity, cardiac myosin light chains (CM-LC), myoglobin (MG), and CK-B isoenzyme were determined in 7 serial blood samples by radioimmunoassays. Measurable amounts of CM-LC were found in at least one serum sample in 13 patients. MG was found to be elevated in 9, and CK-B in 8 of these patients. In the 189 serum samples determined, CM-LC were found more frequently elevated (21.7%) than MG (13.2%, P less than 0.05) or CK-B (12.2%, P less than 0.05). Coronary angiograms were obtained in 21 of the 27 patients. Elevated marker protein concentrations were found only in patients with coronary artery stenosis greater than or equal to 70% of at least one coronary artery. The incidence of elevated serum concentrations of any of the 3 marker proteins determined was higher in patients with 3 vessel disease than in those with 1 or 2 vessel disease (33.9% vs 15.6%, P less than 0.05), and it was higher in patients with a history of previous myocardial infarction than in those without (34.5% vs 11.4%, P less than 0.001). The findings suggest that in a subgroup of patients with angina pectoris at rest but without evidence of acute myocardial infarction, ischaemic damage of small myocardial areas can be detected by serological assays of high sensitivity. Among the marker proteins studied, CM-LC were found the most sensitive.

[Silent ischemia in stable angina pectoris. Characteristics in frequency-modulated long-term ECG]

Frequency-modulated (FM) long-term ECGs, leads CM5 and CC5, were analysed to define the features which characterize silent ischemia in stable angina. Of 40 consecutively examined out-patients with angiographically proven coronary heart disease 22 had more than three ischemia-type episodes, of which at least one each was symptomatic or asymptomatic. Compared with the asymptomatic ones, the symptomatic episodes had significantly more ST deviations of greater than or equal to 0.15 mV (45.5% vs 17.3%; P less than 0.001) or greater than or equal to 0.2 mV (24.2% vs 5.8%; P less than 0.001). Simultaneous ST deviations in both leads were registered more frequently during symptomatic than silent episodes (43.9% vs 22.4%; P less than 0.01). The incidence of prolonged (greater than or equal to 10 min) ST-deviations was not significantly different during symptomatic and asymptomatic episodes (47.0% vs 40.4%; P greater than 0.05). While only 29.7% of all identified episodes were accompanied by symptoms, interindividual comparison indicated that in 63.6% of patients the ischemic episode with maximal ST deviation was symptomatic. It is concluded from these results that in stable angina the occurrence of anginal symptoms is influenced by the intensity and extent of the myocardial ischemia.

[Long-term frequency-modulated ECG recordings after PTCA in a patient with unstable angina pectoris. A case report]

A patient presenting with unstable angina due to severe stenosis of the left anterior descending coronary artery encountered 6 episodes with ST segment depressions greater than or equal to 0.1 mV during frequency-modulated Holter monitoring. Four episodes were associated with anginal pain, 2 were asymptomatic. Percutaneous transluminal coronary angioplasty (PTCA) was performed. During balloon inflations horizontal ST segment depressions occurred. After successful PTCA, the patient remained asymptomatic and no significant ST segment changes were detected by Holter monitoring. Thus, by frequency-modulated Holter monitoring before, during, and after PTCA, the ischaemic cause of episodes with ST segment depressions greater than or equal to 0.1 mV could be demonstrated.

[Sudden cardiac death in long-term electrocardiography]

An analysis has been made of long-term ECG recordings in 11 patients, 9 men and 2 women, mean age 69 +/- 7 years, who were carrying ECG recording equipment at the time of sudden death. Nine patients had coronary heart disease, one patient a dilatative cardiomyopathy and another one a combined aortic valve defect. Seven patients had a history of syncope. All patients had signs of cardiac insufficiency (NYHA index 3.0 +/- 0.6, heart-thorax quotient 0.55 +/- 0.05). Sudden death occurred predominantly whilst resting. In one patient it was due to bradyarrhythmia, in 10 to tachyarrhythmia, mostly ventricular tachycardia (initial heart rate 198 +/- 43/min; n = 8) which degenerated into ventricular fibrillation. Atrial fibrillation was present in 8 patients at the time of sudden death. Premonitory warning arrhythmias were not consistently detectable: comparison of arrhythmias in the first and last hour showed significant increases only in single ventricular extrasystoles (135 vs. 278 VES/h, P less than 0.05), not however in repetitive arrhythmias. An R-on-T phenomenon, as trigger mechanism of ventricular tachycardia, occurred in 5 cases. A synopsis of the published reports on approximately 110 patients with sudden death during long-term electrocardiographic monitoring confirmed that acute death is caused by bradyarrhythmias in approximately 15% (17 patients), and by tachyarrhythmias in 85% (94 patients). An increase in ventricular arrhythmias in the hour prior to death was observed in about 50% of patients and the R-on-T phenomenon, as the initiating mechanism for ventricular tachycardia, in 42%.

[R-wave amplitude during left ventricular volume changes in healthy hearts]

The relationship between R-wave amplitude and left ventricular volume was studied in four tests, each including six normal adults. The means of 10 heart cycles of the R-wave amplitude in surface ECG lead V5 (RV5) and the echocardiographically determined left ventricular enddiastolic dimension (LVEDD) were compared before and during different interventions. After inhalation of 0.3 ml isoamylnitrit, LVEDD was reduced to 7.7%, RV5 to 15.0% below control. During a maneuver of Valsalva, LVEDD decreased to 8.6%, RV5 to 12.9% below control. In both tests heart rates increased markedly. After oral application of propranolol (0.7 to 1.0 mg/kg) LVEDD did not change, whereas RV5 decreased to 8.2% below control. During rapid intravenous infusion of 1 l NaCl 0.9% in 10 to 15 minutes, LVEDD increased to 15.7% above control. R-wave amplitude remained constant. Thus the results of these last two tests let us doubt whether the Brody-effect can be translated without limitation on the in-vivo situation in man.

[ST-segment depression and R-amplitude changes during bicycle stress test in patients with coronary artery disease (author's transl)]

56 patients were examined with bicycle stress tests. Sensitivity and specificity of ST-segment depression were compared with R-wave amplitude changes. All patients had a coronary angiography because of suspected coronary artery disease (CAD). The specificity of ST-segment depression was 71%, for R-wave amplitude changes 50%. The sensitivity for ST-segment depression was 76% and for R-wave amplitude changes 50%. In addition in 7 patients with angiographically demonstrated CAD repeated stress tests were done. The ST-segment changes were nearly constant in all examinations, whereas the R-wave amplitude in V5 in 5 out of 7 patients changed considerably between decrease and increase. Considering these intraindividual changes, it seems doubtful whether the evaluation of the R-wave amplitude proves to be an improvement of the non-invasive diagnostic procedures of CAD.

Influence of endogenous S-adenosylmethionine on the determination of catechol O-methyltransferase activity in red blood cells

A double isotope method for the simultaneous determination of S-adenosylmethionine (SAM) and catechol O-methyltransferase (COMT) activity in red blood cells was developed. Healthy persons contained 7.9 +/- 1.9 nmol SAM per ml red blood cells and 1.9 to 3.8 nmol per ml plasma. Epinephrine increases the SAM biosynthesis rate in red blood cells. The possible influence of endogenous SAM on previous methods to determine COMT activity in red blood cells is discussed. The statement of Briggs and Briggs (Briggs, M.H. and Briggs, M. (1973) Experientia 29, 278--281) that COMT activity in red blood cells is lower during the last 3 months of pregnancy could not be verified by us.