Intravenous thrombolytic treatment for acute myocardial infarction. Effects of early intervention and early examination

Intravenous thrombolytic treatment (streptokinase or anisoylated plasminogen streptokinase activator complex (APSAC) was given to 50 consecutive patients within 3 hours after onset of symptoms of acute myocardial infarction. Left heart catheterisation with coronary angiography and simultaneous double view left ventriculography were performed approximately 4 hours after start of thrombolytic treatment. This examination showed that the acute infarct-related coronary artery was open in 36 patients (72%) and closed in 14 patients (28%). A higher left ventricular ejection fraction was found among patients with open, than among patients with closed infarct-related artery (58.8% vs. 48.4%, p = 0.05). The group with open artery also had a lower score of regional left ventricular dysfunction (1.7 vs. 2.4, p less than 0.05, on a scale from 0-3). Single, double and triple vessel coronary heart disease was found in 22, 14 and 13 patients respectively. Mean age was lower in the group with single vessel disease as compared to double and triple vessel disease (48.4 years vs. 53.4 and 55.4 years, p less than 0.05 and p less than 0.005). Independently of whether the infarct-related artery was open or closed, there tended to be an inverse correlation between number of diseased vessels and preservation of left ventricular function (statistical significance only for single vessel versus triple vessel disease with respect to score of regional left ventricular dysfunction, 1.8 vs. 2.4, p less than 0.05). These findings suggest that early thrombolytic treatment within 3 hours of onset of symptoms may preserve myocardial tissue during the evolution of acute infarction. Furthermore, a presumably better collateralisation from adjacent coronary arteries without stenoses may be important for myocardial preservation. Finally, early angiographic examination can be performed safely and is a good support for determination of further treatment, which in the actual patients was coronary bypass surgery in 8 cases, transluminal angioplasty, PTCA, in 20 cases, and medical treatment alone in 22 cases.

Predictive models of syncope causes in an outpatient clinic

The investigation of unexplained syncope remains a challenging clinical problem. In the present study we sought to evaluate the diagnostic value of a standardized work-up focusing on non invasive tests in patients with unexplained syncope referred to a syncope clinic, and whether certain combinations of clinical parameters are characteristic of rhythmic and reflex causes of syncope.

METHODS AND RESULTS

317 consecutive patients underwent a standardized work-up including a 12-lead ECG, physical examination, detailed history with screening for syncope-related symptoms using a structured questionnaire followed by carotid sinus massage (CSM), and head-up tilt test. Invasive testings including an electrophysiological study and implantation of a loop recorder were only performed in those with structural heart disease or traumatic syncope. Our work-up identified an etiology in 81% of the patients. Importantly, three quarters of the causes were established non invasively combining head-up tilt test, CSM and hyperventilation testing. Invasive tests yielded an additional 7% of diagnoses. Logistic analysis identified age and number of significant prodromes as the only predictive factors of rhythmic syncope. The same two factors, in addition to the duration of the ECG P-wave, were also predictive of vasovagal and psychogenic syncope. These factors, optimally combined in predictive models, showed a high negative and a modest positive predictive value.

CONCLUSION

A standardized work-up focusing on non invasive tests allows to establish more than three quarters of syncope causes. Predictive models based on simple clinical parameters may help to distinguish between rhythmic and other causes of syncope.

Implantation of cardiac resynchronization therapy systems in the CARE-HF trial: procedural success rate and safety

AIMS

To assess procedural characteristics and adjudicated procedure-related (<or=30 days) major adverse events among patients who underwent cardiac resynchronization therapy (CRT) implantation in the CARE-HF study. The CARE-HF study shows that CRT improves symptoms and reduces morbidity and mortality in New York Heart Association (NYHA) class III/IV chronic heart failure (CHF) patients. However, safe and proper implantation of pacing systems remains key to effective CRT delivery.

METHODS AND RESULTS

Generalized linear modeling was used to examine the relationships between first implant success/failure and: NYHA class; beta-adrenergic blocker use; underlying ischemic vs. non-ischemic heart disease; history of coronary artery bypass graft or valve surgery; left ventricular (LV) end-diastolic volume<or=vs. >300 cm(3); and, influence of the participating study-centres. Implantation was attempted in 404/409 patients assigned to CRT, and in 65/404 patients assigned to medical therapy. Among these 469 patients, 450 (95.9%) received a successfully implanted and activated device. Complications occurred within 24 h in 47 patients (10.0%), mainly lead dislodgments (n = 10, 2.1%) and coronary sinus dissection/perforation (n = 10, 2.1%), and between 24 h and 30 days in 26 patients (5.5%), mainly lead dislodgment (n = 13, 2.8%). Mean LV lead stimulation threshold was significantly higher than at the right atrium or right ventricle, though remained stable, delivering effective, and reliable CRT. Implanting experience was the only predictor of procedural outcome.

CONCLUSION

Transvenous CRT system implantation, using a CS lead designed for long-term LV pacing, was safe and reliable. As implanting centres become more experienced, this success rate is expected to increase further.

Gene transfer of RANTES and MCP-1 chemokine antagonists prolongs cardiac allograft survival

Vascularized organ allografts are rapidly destroyed by host immune cells that are recruited along chemokine gradients. Among chemokines, Regulated on Activation, Normal T-cell Expressed and Secreted (RANTES) CC chemokine ligand (CCL5) and monocyte chemoattractant protein (MCP)-1 (CCL2) are upregulated in rejecting cardiac allografts. To antagonize these chemokines, we constructed adenoviral vectors expressing NH(2)-terminal deletion (8ND) mutants of the respective genes. Using the F344-to-LEW rat model, intragraft gene transfer of chemokine analogs prolonged cardiac allograft survival from 10.1+/-0.7 and 10.4+/-0.7 days using non-coding adenovirus and vehicle alone, respectively, to 17.0+/-0.7 days for 8ND-RANTES (P<0.001) and 14.2+/-0.8 days for 8ND-MCP-1 (P<0.01). 8ND-RANTES reduced graft infiltration by monocytes/macrophages, cluster of differentiation (CD) 8alpha(+) and T-cell receptor alphabeta(+) cells, while 8ND-MCP-1 reduced monocytes/macrophages. In mixed leukocyte reactions in vitro, proliferation of host lymphocytes from regional lymph nodes in response to donor splenocytes was unaffected by 8ND-RANTES gene transfer. Using a two-gene approach, the contribution of 8ND-MCP-1 was negligible, consistent with available evidence that 8ND-RANTES inhibits both RANTES and MCP-1 activities. 8ND-RANTES gene transfer and a short course of low-dose cyclosporine A synergistically prolonged graft survival to 37.8+/-5.5 vs 15.4+/-0.5 days with cyclosporine alone (P<0.001). These results suggest a role for anti-chemokine gene therapy as an adjuvant therapy in heart transplantation.

Evaluation of ablation patterns using a biophysical model of atrial fibrillation

Atrial fibrillation (AF) is the most common form of cardiac arrhythmia. Surgical/Radiofrequency (RF) ablation is a therapeutic procedure that consists of creating lines of conduction block to interrupt AF. The present study evaluated 13 different ablation patterns by means of a biophysical model of the human atria. In this model, ablation lines were abruptly applied transmurally during simulated sustained AF, and success rate, time to AF termination and average beat-to-beat interval were documented. The gold standard Cox's Maze III procedure was taken as reference. The effectiveness of twelve less invasive patterns was compared to it. In some of these incomplete lines (entailing a gap) were simulated. Finally, the computer simulations were compared to clinical data. The results show that the model reproduces observations made in vivo: (1) the Maze III is the most efficient ablation procedure; (2) less invasive patterns should include lines in both right and left atrium; (3) incomplete ablation lines between the pulmonary veins and the mitral valve annulus lead to uncommon flutter; (4) computer simulations of incomplete lines are consistent with clinical results of non-transumural RF ablation. Biophysical modeling may therefore be considered as a useful tool for understanding the mechanisms underlying AF therapies.

Baseline characteristics of patients recruited into the CARE-HF study

BACKGROUND

Cardiac resynchronization therapy (CRT) is a promising new treatment for patients with heart failure and cardiac dyssynchrony. The CARE-HF study is a morbidity/mortality trial designed to provide conclusive evidence of the effects of CRT in patients with moderate to severe heart failure.

METHODS

A description of the baseline characteristics of patients randomised in the CARE-HF trial.

RESULTS

813 Patients with predominantly NYHA class III (94%) heart failure were randomised in 82 centres. Their mean age was 65 (interquartile range [IQR] 59 to 72) years, 34% were aged >70 years and 27% were women. Thirty-eight percent of the patients had ischaemic heart disease. Mean heart rate was adequately controlled at 70 (IQR 60 to 78) bpm consistent with the use of beta-blockers. Supine systolic blood pressure was low at 117 (IQR 105 to 130) mm Hg. Eighty-eight percent of patients had a QRS > or =150 ms. Mean LV ejection fraction was 26% (IQR 22 to 29) and end-diastolic dimension was 7.2 (IQR 6.4 to 7.8) cm. Ninety-four percent of patients were receiving loop diuretics, 95% an ACE inhibitor or angiotensin receptor blocker (ARB), 72% a beta-blocker and 56% were taking spironolactone.

CONCLUSIONS

The patients enrolled in CARE-HF had moderately severe heart failure and cardiac dysfunction with evidence of cardiac dyssynchrony. The population appears at high risk of events despite pharmacological therapy and therefore appropriate for a trial of CRT.

[Surgical options for terminal heart failure]

Terminal heart failure can be the cause or the result of major dysfunctions of the organisms. Although, the outcome of the natural history is the same in both situations, it is of prime importance to differentiate the two, as only heart failure as the primary cause allows for successful mechanical circulatory support as bridge to transplantation or towards recovery. Various objective parameters allow for the establishment of the diagnosis of terminal heart failure despite optimal medical treatment. A cardiac index <2.0 l/min, and a mixed venous oxygen saturation <60%, in combination with progressive renal failure, should trigger a diagnostic work-up in order to identify cardiac defects that can be corrected or to list the patient for transplantation with/without mechanical circulatory support.

[What do we actually know about out-of-hospital cardiac arrest?]

Each year at least 300,000 people in the United States and 8000 to 10,000 people in Switzerland suffer from out-of-hospital cardiac arrest, mostly due to ventricular fibrillation. Early defibrillation provides definitive treatment for most of cardiac arrest victims. Semi-automatic external defibrillators are easy to handle devices allowing to deliver an early electric shock and can be successfully used by lay people following minimal training. Newer strategies of defibrillation designed to respond faster to out-of-hospital cardiac arrest, including public access defibrillation, as well as improvement of each link of the chain of survival appears as the best strategy for the management of out-of-hospital cardiac arrest.

[Cardiology]

The therapeutic acquisition to be retained for 2004 are: 1. The elderly patients with heart failure also should receive beta blocker treatment. The correction of anaemia, aggravating factor in heart failure, improves symptoms and survival of the patient. 2. It remains to prove that the treatment of sleep apnea, which seems to be an additional factor for mortality in cardiovascular diseases, is able to reduce the risk. 3. The interventions in the endocanabinoïd system which regulates weight and metabolic processes might be a promising new therapeutic acquisition. 4. Prevention of coronary disease with lipid lowering drugs is still a major topic, and the trend goes the lower the better. The problems observed with Rofecoxybe and other drug interactions reminds us to be conscious when prescribing multiple drugs. 5. The implantable defibrillator seems to be a life insurance in the event of ventricular fibrillation. However, it is not so easy to identify the patient who might really benefit.

Localization and quantification of mitral valve prolapse using three-dimensional echocardiography

AIMS

Mitral valve prolapse is a common source of severe mitral regurgitation in Western countries. Three-dimensional echocardiography can provide views of the entire valve, allowing a complete assessment of the valve leaflets and commissures. It has the potential to precisely locate and quantify mitral valve prolapse.

METHODS AND RESULTS

Between January 1997 and December 2000, 91 patients with severe mitral regurgitation due to mitral valve prolapse underwent a transesophageal echocardiography with three-dimensional reconstruction of the mitral valve as part of their pre-operative work-up. The location and extent of the prolapse by echo was compared to the surgical status. The volume of prolapsing leaflet was calculated and compared to the volume of resected tissue whenever a repair was attempted. There was an excellent correspondence between the echographic localization of the prolapse and surgical inspection, and between the volume of prolapsing and surgically resected tissue (r=0.94, p<0.0001).

CONCLUSIONS

In patients with severe mitral regurgitation due to mitral valve prolapse, 3D echo allowed a precise localization and an accurate quantification of the prolapsing portion of the leaflets. This technique can provide refinements in the surgical planning of mitral valve repair and in the selection of candidates for this intervention.

Alloimmunity and nonimmunologic risk factors in cardiac allograft vasculopathy

Graft vasculopathy is an accelerated form of coronary artery disease that occurs in transplanted hearts. Despite major advances in immunosuppression, the prevalence of the disease has remained substantially unchanged during the last two decades. According to the 'response to injury' paradigm, graft vasculopathy is the result of a continuous inflammatory response to tissue injury initiated by both alloantigen-dependent and independent stress responses. Experimental evidence suggests that these responses may become self-sustaining, as allograft re-transplantation into the donor strain at a later stage fails to prevent disease progression. Histological evidence of endothelitis and arteritis, in association with intima fibrosis and atherosclerosis, reflects the central role of alloimmunity and inflammation in the development of arterial lesions. Experimental results in gene-targeted mouse models indicate that cellular and humoral immune responses are both involved in the pathogenesis of graft vasculopathy. Circulating antibodies against donor endothelium are found in a significant number of patients, but their pathogenic role is still controversial. Alloantigen-independent factors include donor-transmitted coronary artery disease, surgical trauma, ischaemia-reperfusion injury, viral infections, hyperlipidaemia, hypertension, and glucose intolerance. Recent therapeutic advances include the use of novel immunosuppressive agents such as sirolimus (rapamycin), HMG-CoA reductase inhibitors, calcium channel blockers, and angiotensin converting enzyme inhibitors. Optimal treatment of cardiovascular risk factors remains of paramount importance.

Ectopic pacing at physiological rate improves postanoxic recovery of the developing heart

Recently, rapid and transient cardiac pacing was shown to induce preconditioning in animal models. Whether the electrical stimulation per se or the concomitant myocardial ischemia affords such a protection remains unknown. We tested the hypothesis that chronic pacing of a cardiac preparation maintained in a normoxic condition can induce protection. Hearts of 4-day-old chick embryos were electrically paced in ovo over a 12-h period using asynchronous and intermittent ventricular stimulation (5 min on-10 min off) at 110% of the intrinsic rate. Sham (n = 6) and paced hearts (n = 6) were then excised, mounted in vitro, and subjected successively to 30 min of normoxia (20% O(2)), 30 min of anoxia (0% O(2)), and 60 min of reoxygenation (20% O(2)). Electrocardiogram and atrial and ventricular contractions were simultaneously recorded throughout the experiment. Reoxygenation-induced chrono-, dromo-, and inotropic disturbances, incidence of arrhythmias, and changes in electromechanical delay (EMD) in atria and ventricle were systematically investigated in sham and paced hearts. Under normoxia, the isolated heart beat spontaneously and regularly, and all baseline functional parameters were similar in sham and paced groups (means +/- SD): heart rate (190 +/- 36 beats/min), P-R interval (104 +/- 25 ms), mechanical atrioventricular propagation (20 +/- 4 mm/s), ventricular shortening velocity (1.7 +/- 1 mm/s), atrial EMD (17 +/- 4 ms), and ventricular EMD (16 +/- 2 ms). Under anoxia, cardiac function progressively collapsed, and sinoatrial activity finally stopped after approximately 9 min in both groups. During reoxygenation, paced hearts showed 1) a lower incidence of arrhythmias than sham hearts, 2) an increased rate of recovery of ventricular contractility compared with sham hearts, and 3) a faster return of ventricular EMD to basal value than sham hearts. However, recovery of heart rate, atrioventricular conduction, and atrial EMD was not improved by pacing. Activity of all hearts was fully restored at the end of reoxygenation. These findings suggest that chronic electrical stimulation of the ventricle at a near-physiological rate selectively alters some cellular functions within the heart and constitutes a nonischemic means to increase myocardial tolerance to a subsequent hypoxia-reoxygenation.

[Left ventricular hypertrophy: a marker for patients at risk of arterial hypotension during stress echocardiography with dobutamine?]

OVERVIEW

Arterial hypotension during stress echocardiography with Dobutamine (ESD) is an occasional complication with no prognostic value, but it sometimes necessitates termination of the investigation. The present study had the aim of elucidating the mechanism responsible for hypotension during ESD and proposing one or several markers for patients at risk for this complication.

METHOD

One hundred and twenty consecutive patients referred for stress echocardiography (Dobutamine or cycloergometrine) were analysed. Arterial hypotension induced by Dobutamine was defined as a fall of more than 30 mmHg compared to the arterial pressure before the test or following the preceding level of Dobutamine. Concentric left ventricular hypertrophy (LVH) was defined as a left ventricular mass > 125 g/m2.

RESULTS

Among the 89 patients undergoing ESD, 32 (35%) had LVH, 9 of whom (28%) had arterial hypotension, prompting termination of the examination in 4 patients. Among the 57 patients (65%) without LVH, only 2 (3%) had hypotension. All patients with LVH had normal left ventricular function at rest and excellent contractility under stress, with no sign of ischaemia. None of the 31 patients, 5 of whom had LVH, who underwent the test with cycloergometrine had hypotension.

CONCLUSION

Hypotension occurring during ESD affects patients more often with LVH (p < 0.001) and excellent systolic function. We postulate that the vigorous contraction of the left ventricle with Dobutamine produces excessive stimulation of the cardiac mechanoreceptors inducing a reflex hypotension. LVH is therefore a marker for patients at risk of hypotension and effort echocardiography is an excellent alternative to this investigation.

Study of atrial arrhythmias in a computer model based on magnetic resonance images of human atria

The maintenance of multiple wavelets appears to be a consistent feature of atrial fibrillation (AF). In this paper, we investigate possible mechanisms of initiation and perpetuation of multiple wavelets in a computer model of AF. We developed a simplified model of human atria that uses an ionic-based membrane model and whose geometry is derived from a segmented magnetic resonance imaging data set. The three-dimensional surface has a realistic size and includes obstacles corresponding to the location of major vessels and valves, but it does not take into account anisotropy. The main advantage of this approach is its ability to simulate long duration arrhythmias (up to 40 s). Clinically relevant initiation protocols, such as single-site burst pacing, were used. The dynamics of simulated AF were investigated in models with different action potential durations and restitution properties, controlled by the conductance of the slow inward current in a modified Luo-Rudy model. The simulation studies show that (1) single-site burst pacing protocol can be used to induce wave breaks even in tissue with uniform membrane properties, (2) the restitution-based wave breaks in an atrial model with realistic size and conduction velocities are transient, and (3) a significant reduction in action potential duration (even with apparently flat restitution) increases the duration of AF. (c) 2002 American Institute of Physics.

[Out of hours coronary angiography: changing indications]

The authors have recently demonstrated that 13% of indications for cardiac catheterisation performed "after hours" (week ends, holidays or from 6 pm to 7 am) are Class III of the AHA/ACC recommendations (i.e. indications not based on recognised medical evidence). In order to limit procedures performed for these unrecognised indications, a consensus of experts has defined a number of local recommendations. The aim of this paper was to study the impact of these recommendations on the indications of "out of hours" cardiac catheterisation. Two patient populations were identified and compared with respect to these recommendations. The first group comprised 157 consecutive patients treated between 1993 and 1994 (average age 58 +/- 13 years; 35% females) and the second one of 148 consecutive patients treated from 1998 to 1999 (average age 57 +/- 13 years; 25% females). The local recommendations were respected in 61% of cases and not applied in 39% of cases. This was a satisfactory result in view of the fact that the local recommendations are more restrictive than international guidelines as they cover emergency indications. In the second group of patients, there were no AHA/ACC Class III indications (30% Class I, 6% Class IIa and 3% Class IIb). There was a significant increase in the number of primary angioplasties for acute myocardial infarction (27 vs 2%; p < 0.001) and an expected reduction in salvage angioplasties (17 vs 7%; p < 0.01). There was no significant change in the indications in patients with unstable angina, the European and American guidelines having been published at the end of data collection. Therefore, the introduction of recommendations for out of hours cardiac catheterisation has limited the number performed for unrecognised indications in favour of evidence based procedures.

Silent single coronary artery anomaly depicted by magnetic resonance angiography

Coronary artery anomalies are rare and usually benign. They are detected by coronary angiograms during invasive catheterization. Single coronary artery anomaly, with the left main artery originating from the proximal right coronary artery, can be responsible for myocardial blood supply insufficiency and causes chest pain or sudden death, especially during physical exercise, as it courses between the aorta and the pulmonary artery. We report a case of a fortuitous diagnosis of single coronary artery anomaly discovered during coronary angiogram and investigated in addition with magnetic resonance angiography. Magnetic resonance imaging can provide a precise description of the coronary artery anomaly and its course between great arteries, allowing accurate surgical planning.

Incessant atrioventricular dissociation due to far-field QRS oversensing and recurrent mode switch in a dual chamber pacemaker

We report the case of a repetitive and incessant activation of mode switch in a dual chamber pacemaker because of the inappropriate sensing by the atrial lead of far-fields signals from the ventricular evoked response. The incidence, consequences and prevention of the oversensing of far-field QRS complexes are discussed.

A computer model of human atria with reasonable computation load and realistic anatomical properties

Atrial fibrillation is the most frequent arrhythmia, provoking discomfort, heart failure and arterial embolisms. The aim of this work is to develop a simplified anatomical computer model of human atria for the study of atrial arrhythmias and the understanding of electrical propagation mechanisms. With the model we propose, up to 40 s of real-time propagation have been simulated on a single-processor computer. The size and the electrophysiological properties of the simulated atria are within realistic values and information about anatomy has been taken into account in a three-dimensional structure. Besides normal sinus beat, pathological phenomena such as flutter and fibrillation have been induced using a programmed stimulation protocol. One important observation in our model is that atrial arrhythmias are a combination of functional and anatomical reentries and that the geometry plays an important role. This virtual atrium can reproduce electrophysiological observations made in humans but with the advantage of showing in great detail how arrhythmias are initiated and sustained. Such details are difficult or impossible to study in humans. This model will serve us as a tool to evaluate the impact of new therapeutic strategies and to improve them.

The CARE-HF study (CArdiac REsynchronisation in Heart Failure study): rationale, design and end-points

BACKGROUND

Cardiac resynchronisation is a promising new intervention for patients with heart failure, left ventricular systolic dysfunction and ventricular dyssynchrony.

OBJECTIVE

The CARE-HF trial is designed to evaluate the long-term effects of cardiac (atrio-bi-ventricular) resynchronisation on the mortality and morbidity of patients with heart failure due to left ventricular systolic dysfunction already receiving diuretics and optimal medical therapy with ACE inhibitors and beta-blockers (where indicated and tolerated).

METHODS AND RESULTS

Approximately 800 patients will be randomised to device therapy or control and followed for a minimum of 18 months. A pragmatic study design has been chosen that does not attempt to conceal allocation from investigators or patients because it is impossible to guarantee maintenance of blinding for the duration of the study. The end-points committee will adjudicate events in a blinded fashion. Since cardiac resynchronisation may alter other aspects of the management of the patient, as would occur in clinical practice, the study should be considered a comparison of strategies rather than simply of a device. The primary end-point is all-cause mortality or unplanned cardiovascular hospitalisation. The study should complete recruitment during 2002 and report in 2004.

The World Survey of Cardiac Pacing and Implantable Cardioverter Defibrillators: calendar year 1997--Europe

The registry of the European Working Group on Cardiac Pacing (EWGCP) is based on the European Pacemaker Identification Card originally designed in July 1978. National registration centers collect the local data and send aggregated annual data to the EWGCP. For 1997, data were obtained from 2,887 hospitals in 20 European countries representing a population of 568 million. Across all participating countries, the median value for all implanted pacemakers was 378 per million population. For initial pacemaker implants, the median value was 290 per million population. Single chamber atrial pacing was important in Denmark, the Netherlands, Poland, Slovak Republic, Spain, and Sweden for the treatment of sick sinus syndrome. Dual chamber pacing accounted for < 50% of initial implants in only 5 of 14 countries for atrioventricular block, and in only 3 of 15 countries for sick sinus syndrome. In 7 of 15 countries, unipolar ventricular leads were used in > or = 50% of cases. In 6 of 14 countries, there was > 15% use of unipolar atrial leads. Nine of 13 countries frequently used atrial active-fixation leads. For the 1997 survey, ICD data were obtained from 16 countries. The total number of ICDs per million population was a median value of 14. Initial ICD implants per million population was 11. Only 3 of 16 countries implanted a total of 30 or more ICDs per million population. Pacing and ICD practices were dependent on the availability of medical and technical resources and influenced by economic constraints inherent in health care administration and insurance coverage patterns.

[Implantable defibrillator. Update]

The implantable cardioverter-defibrillator is a device able to detect and efficiently treat life-threatening ventricular arrhythmias. Its decisive accomplishment in reducing sudden cardiac death and total cardiac mortality, opposed to the insufficient reliability of the traditional therapies explains its present ascendancy. In this review, the working principles and the implant techniques are developed, as well as the complications and the usual problems which could be encountered in implanted patients. Finally, the current indications are discussed in the light of recent clinical trials.

Effects of multisite biventricular pacing in patients with heart failure and intraventricular conduction delay

BACKGROUND

One third of patients with chronic heart failure have electrocardiographic evidence of a major intraventricular conduction delay, which may worsen left ventricular systolic dysfunction through asynchronous ventricular contraction. Uncontrolled studies suggest that multisite biventricular pacing improves hemodynamics and well-being by reducing ventricular asynchrony. We assessed the clinical efficacy and safety of this new therapy.

METHODS

Sixty-seven patients with severe heart failure (New York Heart Association class III) due to chronic left ventricular systolic dysfunction, with normal sinus rhythm and a duration of the QRS interval of more than 150 msec, received transvenous atriobiventricular pacemakers (with leads in one atrium and each ventricle). This single-blind, randomized, controlled crossover study compared the responses of the patients during two periods: a three-month period of inactive pacing (ventricular inhibited pacing at a basic rate of 40 bpm) and a three-month period of active (atriobiventricular) pacing. The primary end point was the distance walked in six minutes; the secondary end points were the quality of life as measured by questionnaire, peak oxygen consumption, hospitalizations related to heart failure, the patients' treatment preference (active vs. inactive pacing), and the mortality rate.

RESULTS

Nine patients were withdrawn from the study before randomization, and 10 failed to complete both study periods. Thus, 48 patients completed both phases of the study. The mean distance walked in six minutes was 22 percent greater with active pacing (399+/-100 m vs. 326+/-134 m, P<0.001), the quality-of-life score improved by 32 percent (P<0.001), peak oxygen uptake increased by 8 percent (P<0.03), hospitalizations were decreased by two thirds (P<0.05), and active pacing was preferred by 85 percent of the patients (P<0.001).

CONCLUSIONS

Although it is technically complex, atriobiventricular pacing significantly improves exercise tolerance and quality of life in patients with chronic heart failure and intraventricular conduction delay.

Pacing redistributes glycogen within the developing myocardium

Electrical pacing at physiological rate induces myocardial remodeling associated with regional changes in workload, blood flow and oxygen consumption. However, to what extent energy-producing pathways are also modified within the paced heart remains to be investigated. Pacing could particularly affect glycogen metabolism since hypertrophy stimulates glycolysis and increased workload favors glucose over fat oxidation. In order to test this hypothesis, we used the embryonic chick heart model in which ventricular pacing rapidly resulted in thinning of the ventricle wall and thickening of the atrial wall. Hearts of stage 22HH chick embryos were submitted in ovo to asynchronous and intermittent ventricular pacing delivered at physiological rate during 24 h. The resulting alterations of glycogen content were determined in atrium, ventricle and conotruncus of paced and sham-operated hearts. Hemodynamic parameters of the paced and spontaneously beating hearts were derived from computerized image analysis of video recordings. With respect to sham, paced hearts showed a significant decrease in glycogen content (nmoles glucose units/microg protein; mean+/-S.D.) only in atrium (1.48+/-0.40 v 0.84+/-0.34, n=8) and conotruncus (0.75+/-0.28 v 0.42+/-0.23, n=8). Pacing decreased the end diastolic and stroke volumes by 34 and 44%, respectively. Thus, the rapid glycogen depletion in regions remote from the stimulation site appears to be associated with regional changes in workload and remodeling. These findings underscore the importance of the coupling mechanisms between metabolic pathways and myocardial remodeling in the ectopically paced heart.

Evidence rather than costs must guide use of the implantable cardioverter defibrillator

Randomized controlled trials have shown superior survival rates with implantable cardioverter defibrillators (ICDs) compared with antiarrhythmic drugs in survivors of cardiac arrest and life-threatening ventricular tachyarrhythmias, as well as in high-risk patients with ischemic heart disease and inducible ventricular tachycardia (VT). Current defibrillators are small and implanted with techniques similar to standard pacemakers. They provide high-energy shocks for ventricular fibrillation (VF) and rapid VT, antitachycardia pacing for monomorphic VT, and antibradycardia pacing. Limited evidence suggests that ICD therapy is cost-effective when compared with other widely accepted treatments. The use of ICDs is likely to continue to expand in the future. Ongoing clinical trials will define further prophylactic indications of the ICD and clarify its cost-effectiveness ratio in different clinical settings.

High prevalence of peripheral atherosclerosis in a rapidly developing country

Cardiovascular disease is rapidly increasing in developing countries experiencing epidemiological transition. We investigated the prevalence of peripheral atherosclerosis in a rapidly developing country and compared our findings with data previously reported in Western populations. A cardiovascular risk factor survey was conducted in 1067 individuals aged 25-64 randomly selected from the general population of Seychelles. High-resolution ultrasonography of the right and left carotid and femoral arteries was performed in a random subgroup of 503 subjects (245 men and 258 women). In each of the four arteries, arterial wall thickness (in plaque-free segments) and atherosclerotic plaques (i.e. focal wall thickening at least 1.0 mm thick) were measured separately. The prevalence of peripheral atherosclerosis was high in this population. For instance, at least one plaque > or =1.0 mm was found in, respectively, 34.9 and 27.5% of men and women aged 25-34 and at least one plaque > or =2.5 mm was found in, respectively, 58.2 and 36.9% of men and women aged 55-64. With reference to data found in the literature, the prevalence of carotid atherosclerosis appeared to be significantly higher in Seychelles than in Western populations. This study provides further evidence for the importance of cardiovascular disease in developing countries. Determinants should be identified and relevant prevention and control programs implemented.

Implantation of a cardiac resynchronization system for idiopathic dilated cardiomyopathy in a patient with persistent left superior vena cava using an experimental lead for left ventricular stimulation

A persistent left superior vena cava (PLSVC) was discovered at the implantation of a cardiac resynchronization system in a woman with an idiopathic dilated cardiomyopathy. Standard leads were used to obtain right ventricular and right atrial (RA) stimulation according to a formerly described technique. The left ventricle was stimulated through the posterolateral vein of the heart by a novel lead design to be used over a guidewire for placement. Despite expected difficulties in this anatomic situation, the research lead was positioned in 23 minutes.

Performance of classic electrocardiographic criteria for left ventricular hypertrophy in an African population

ECG criteria for left ventricular hypertrophy (LVH) have been almost exclusively elaborated and calibrated in white populations. Because several interethnic differences in ECG characteristics have been found, the applicability of these criteria to African individuals remains to be demonstrated. We therefore investigated the performance of classic ECG criteria for LVH detection in an African population. Digitized 12-lead ECG tracings were obtained from 334 African individuals randomly selected from the general population of the Republic of Seychelles (Indian Ocean). Left ventricular mass was calculated with M-mode echocardiography and indexed to body height. LVH was defined by taking the 95th percentile of body height-indexed LVM values in a reference subgroup. In the entire study sample, 16 men and 15 women (prevalence 9.3%) were finally declared to have LVH, of whom 9 were of the reference subgroup. Sensitivity, specificity, accuracy, and positive and negative predictive values for LVH were calculated for 9 classic ECG criteria, and receiver operating characteristic curves were computed. We also generated a new composite time-voltage criterion with stepwise multiple linear regression: weighted time-voltage criterion=(0.2366R(aVL)+0.0551R(V5)+0.0785S(V3)+ 0.2993T(V1))xQRS duration. The Sokolow-Lyon criterion reached the highest sensitivity (61%) and the R(aVL) voltage criterion reached the highest specificity (97%) when evaluated at their traditional partition value. However, at a fixed specificity of 95%, the sensitivity of these 10 criteria ranged from 16% to 32%. Best accuracy was obtained with the R(aVL) voltage criterion and the new composite time-voltage criterion (89% for both). Positive and negative predictive values varied considerably depending on the concomitant presence of 3 clinical risk factors for LVH (hypertension, age >/=50 years, overweight). Median positive and negative predictive values of the 10 ECG criteria were 15% and 95%, respectively, for subjects with none or 1 of these risk factors compared with 63% and 76% for subjects with all of them. In conclusion, the performance of classic ECG criteria for LVH detection was largely disparate and appeared to be lower in this population of East African origin than in white subjects. A newly generated composite time-voltage criterion might provide improved performance. The predictive value of ECG criteria for LVH was considerably enhanced with the integration of information on concomitant clinical risk factors for LVH.

[Pacemaker therapy of hypertrophic obstructive cardiomyopathy. PIC (Pacing in Cardiomyopathy) Study Group]

Clinical management of patients with symptoms caused by pharmacological refractory hypertrophic obstructive cardiomyopathy must consider surgical myectomy, percutaneous transluminal septal myocardial ablation and implantation of a DDD pacemaker. Until now, no prospective, double blind, randomized studies have yet been carried out to determine the merits of each of these treatment alternatives. However, uncontrolled studies have shown that short atrioventricular delay dual-chamber pacing reduces outflow tract obstruction. Aim of the study was to investigate the results of the pacemaker therapy in a prospective, double blind randomized crossover procedure. All patients with hypertrophic obstructive cardiomyopathy included in this multicenter study were either refractory or intolerant to drugs and typically had pressure gradients higher than 30 mm Hg. In 83 patients, mean age 53 (18 to 82) years who responded favorably to a temporary pacing test, a DDD pacemaker was implanted. After echo- and echo-Doppler-based measurements of hemodynamic parameters the patients were randomized into 2 groups, those with an implanted pacemaker in the inactivated mode (AAI) and those with a pacemaker in the activated mode (DDD with optimized short AV delay). A crossover of these groups was performed after 12 and 24 weeks, respectively. Both objective parameters of echo including Doppler, and spiroergometry, and subjective parameters of angina, dyspnea, and quality of life were recorded. Additionally, subgroups based on age decades were analyzed. After 12 weeks in the DDD mode, regardless of the randomization sequence, a decrease of the pressure gradient from 59 +/- 36 mm Hg (median) to 30 +/- 25 mm Hg was proven significant (p < 0.001). The endurance of the patients who, during screening, achieved less than 10 minutes of exercise by the Bruce protocol improved by 21% under DDD mode. The main symptoms, as measured by the NYHA classification, improved statistically significant from a mean of 2.4 to 1.7 for functional class, from a mean of 2.4 to 1.4 for dyspnea and from a mean of 1.0 to 0.4 for angina. Subgroup analysis showed improvements depended significantly upon age, with a marked improvement between the ages of 60 and 70, which was statistically significant as compared to other decades. Subjective improvements in the quality-of-life of patients was measured using a specially developed questionnaire. These findings justify, by all means, the intention to implant a DDD pacemaker in older patients. In younger and/or such patients with elevated pressure gradients, the results of ongoing randomized studies comparing myectomy, PTSMA and pacing have to be considered.

[Reference values of intima-medial thickness of carotid and femoral arteries in subjects aged 20 to 60 years and without cardiovascular risk factors]

Many studies have shown a close correlation between intima-medial thickness of the carotid artery measured by high resolution ultrasonography and the presence of coronary artery disease or atherogenic risk factors. However, reference values for the value of intima-medial thickness (IMT) in healthy subjects have not yet been established. The aim of this study was, therefore, to determine the reference values of carotid (C-IMT) and femoral intima-medial thickness (F-IMT) with respect to age and gender in healthy subjects (53 women and 45 men) aged 20 to 60, with no family or personal history of cardiovascular disease or atherogenic risk factors, underwent high resolution colour echo-Doppler examination. The mean C-IMT was 556 +/- 57 microns in women and 573 +/- 70 microns in men (NS), and the femoral equivalent was 543 +/- 63 microns in women and 562 +/- 74 microns in men (NS). Between the ages of 20 and 60, the C-IMT increased by 1.8 microns per year (p < 0.03) in women and 3.4 microns (p < 0.001) in men, the variations being respectively 1.2 microns (NS) and 3.1 microns (p < 0.002) in the femoral artery. Multiple regression analysis including gender and individual values of age, body mass index and lipid profile confirmed that only age was significantly correlated to the increase in thickness. The authors conclude that the reference values of IMT do not differ with gender or site of analysis, but there is a slight influence with respect to age.

Developing clinical indication for multisite pacing

The artificial activation of the heart modifies the mechanics of contraction and relaxation. While only little basic research has been addressed to this question, clinical observations showed that for hypertrophic as well as dilated cardiomyopathies appropriate pacing techniques can be useful. Pacing can influence the activation sequence. The spread out from a single site is slow, and so hypercontractility deminshed. With the use of multiple electrodes, two atrial and/or two ventricular, conduction delays in the atria or ventricles can be eliminated. Synchronisation of the cardiac activation has an anti-arrhythmic and positiv inotropic effect. This may lead to new indications for pacemakers or better to be named cardiac synchronisers.

Electrocardiographic findings in a middle-aged African population in the Seychelles islands

This study describes major electrocardiogram (ECG) measurements and diagnoses in a population of African individuals; most reference data have been collected in Caucasian populations and evidence exists for interethnic differences in ECG findings. This study was conducted in the Seychelles islands (Indian Ocean) and included 709 black individuals (343 men and 366 women) aged 25 to 64 years randomly selected from the general population. Resting ECG were recorded by using a validated ECG unit equipped with a measurement and interpretation software (Cardiovit AT-6, Schiller, Switzerland). The epidemiology of 14 basic ECG measurements, 6 composite criteria for left ventricular hypertrophy and 19 specific ECG diagnoses including abnormal rhythms, conduction abnormalities, repolarization abnormalities, and myocardial infarction were examined. Substantial gender and age differences were found for several ECG parameters. Moreover, tracings recorded in African individuals of the Seychelles differed from those collected similarly in Caucasian populations in many respects. For instance, heart rate was approximately 5 beats per minute lower in the African individuals than in selected Caucasian populations, prevalence of first degree atrio-ventricular block was especially high (4.8%), and the average Sokolow-Lyon voltage was markedly higher in African individuals of the Seychelles compared with black and white Americans. The integrated interpretation software detected "old myocardial infarction" in 3.8% of men and 0% of women and "old myocardial infarction possible" in 6.1% and 3%, respectively. Cardiac infarction injury scores are also provided. In conclusion, the study provides reference values for ECG findings in a specific population of people of African descent and stresses the need to systematically consider gender, age, and ethnicity when interpreting ECG tracings in individuals.

Usefulness of the echocardiographic velocity ratio for detection of significant aortic stenosis

In this study, which included 56 patients with aortic stenosis, the predictive value of the fractional shortening velocity ratio was evaluated. This Doppler index allowed detection of significant aortic stenosis (0.53 cm2/m2), with a positive predictive value of 93% and a negative predictive value of 92% for a cutoff value of 0.8.

[Cardiac pacing. Percutaneous extraction of infected pacing catheter]

Infection of a cardiac pacemaker is a rare but serious complication. Percutaneous ablation of the pacemaker and pacing catheter is the only effective treatment. Techniques of extraction of pacing systems have been evaluated but the long term results require analysis. Eighteen patients with infection of cardiac pacemakers underwent extraction of one or more pacing catheters (14 atrial and 20 ventricular) in one same centre. The indication was infection of the pacemaker unit (12 cases) or septicaemia (6 cases) The causal organism was a staphylococcus (aureus: 7 cases, epidermidis: 10 cases, capitis: 1 case). Three techniques were used: 1) direct external manual traction, 2) internal traction with several devices, 3) endovascular counter-traction (Byrd-Cook system). The time from primary implantation of the pacing catheter to its extraction was 42 months and from last pacemaker manipulation to infection, 23 months. The average duration of the extraction procedure was 120 +/- 45 minutes; that of fluoroscopy was 10 +/- 6 minutes. The first technique was used 12 times, the second 8 times and the third 14 times, with complete extraction of the catheter in 88.2% of cases. The metallic tip of the distal electrode embolised in 2 cases and remained stuck in the right ventricle in 1 case. Only one pacing catheter was abandoned. After an average follow-up of 45 months, none of the patients had recurrent infection or any other complication. The authors conclude that extraction of infected pacing catheters is safe and effective. It is the treatment of choice of this complication.

Recurrent cardioembolic stroke related to late dislodgement of a right atrial pacing lead into the left atrium

A 76-year-old woman had a permanent transvenous DDDR pacemaker implanted for complete atrioventricular block. She was hospitalized 4 years later for recurrent transient ischaemic attacks related to dislodgment of the atrial lead into the left atrium through a patent foramen ovale. The patient was successfuly treated by transvenous extraction of the atrial lead. The follow-up has been uneventful 12 months after the procedure. Left atrially dislodged pacemaker leads have to be retracted under full anticoagulation.

Significant improvement of quality of life following atrioventricular synchronous pacing in patients with hypertrophic obstructive cardiomyopathy. Data from 1 year of follow-up. PIC study group. Pacing In Cardiomyopathy

AIMS

Atrioventricular synchronous pacing exerts beneficial effects, including reduction of left ventricular outflow tract gradients, in patients with hypertrophic obstructive cardiomyopathy. The Pacing in Cardiomyopathy study was initiated to explore the effects of pacing in a double-blind randomized crossover fashion. The aims were to ascertain the beneficial effects of pacing in a controlled study and to rule out a placebo effect by pacing. This paper deals with the outcome of pacing on quality of life during 1 year of follow-up.

METHODS

Quality of life was evaluated with the Karolinska questionnaire, validated for patients paced for bradyarrhythmias and ischaemic heart disease. Drug-refractory patients with hypertrophic obstructive cardiomyopathy were recruited for the study and after a temporary pacing procedure implanted with permanent pacemakers. Patients were randomized to two study arms defining the sequence of pacemaker programming. In one arm the pacemaker was inactive, in the other active. After 3 months the pacemaker was reprogrammed to the alternate mode and a further 3 months followed. After this period subsequent pacemaker programming corresponded to the mode preferred by the patient. A last assessment was made 1 year after baseline examinations.

RESULTS

Eighty patients completed the first crossover period and 75 completed the full 1 year of follow-up. Active pacing induced significant quality of life improvements, in the order of 9-44%, regardless of programming sequence. Discontinuation of pacing after a first active period resulted in the return of symptoms. Fourteen patients requested early reprogramming after having been programmed to inactive pacing after a first period of active pacing. Seventy-six patients preferred active pacing after the crossover period. A further 6 months of pacing induced progressive improvement in symptoms already favourably influenced.

CONCLUSION

Atrioventricular synchronous pacing has a profound beneficial effect on most domains of quality of life in patients with hypertrophic obstructive cardiomyopathy refractory to drug treatment.

Five-year outcome in patients with isolated proximal left anterior descending coronary artery stenosis treated by angioplasty or left internal mammary artery grafting. A prospective trial

BACKGROUND

Percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass surgery (CABG) improve the clinical status of patients with isolated proximal left anterior descending coronary artery stenosis. At 2 years, only additional revascularization was more frequently required after PTCA.

METHODS AND RESULTS

We monitored 134 patients randomized to PTCA (n=68) or CABG (n=66) for </=5 years. End points were death, myocardial infarction, need for additional revascularization, clinical status, and medical treatment. At 5 years, 6 patients (9%) had died in the PTCA group versus 2 (3%) in the CABG group (P=0.12). One patient in each group died of a cardiac cause. Myocardial infarction was more frequent after PTCA (15% versus 4%; P=0.0001), but Q-wave infarction was not (6% in the PTCA group versus 3% in the CABG group; P=0.8). Additional revascularization was required in 38% of patients in the PTCA group versus 9% in the CABG group (P=0.0001). Functional status was comparable, with 6% of patients after PTCA and 3% after CABG in functional class III or IV. Finally, after PTCA or CABG, 62% and 91% of patients, respectively, were free of events (P=0.0001).

CONCLUSIONS

The 5-year prognosis of patients with isolated proximal left anterior descending coronary artery stenosis is good. Both PTCA and CABG improve clinical status, but revascularization was needed more frequently after PTCA. There is an excess incidence of non-Q-wave myocardial infarction in the PTCA group that does not affect the vital or symptomatic outcome.

Pacing-induced ventricular remodeling in the chick embryonic heart

Chronic ectopic pacing in the adult heart induces myocardial hypotrophy close to the pacing site. We have recently described a similar localized decrease of compact myocardium thickness in the chick embryonic heart after 48 h of intermittent apical ventricular pacing. Here we analyze the cellular mechanisms underlying the response of the embryonic heart to pacing. Because the developing heart had been found to adjust its morphology according to functional demands by undergoing cellular hyperplasia or hypoplasia, we hypothesized that the stimulation should result in hypoplasia of the apical ventricular compartment. Morphologic analysis of hearts submitted to 18 h of effective pacing during 48 h showed a mild to moderate ventricular dilatation, a 28% decrease in the apical compact layer thickness with no changes in other ventricular locations, and atrial wall thickening. These modifications were caused by changes in the number of cell layers, whereas cell size was similar between paced and control hearts. Analysis of proliferative activity after 24 h of pacing showed a decrease of 32% in the rate of cell proliferation limited to the apical compact layer exposed to stimulation. No ultrastructural injury or increased cell death was found. These changes were accompanied by down-regulation of the myocardial growth factor fibroblast growth factor-2 but no differences were found in the expression of platelet-derived growth factor. Thus, chronic intermittent ventricular pacing induces myocardial remodeling in the chick embryonic heart, on the basis of locally regulated rates of cell proliferation.