The implantable defibrillator and return to operation of vehicles study.

AIMS: We sought to characterise driving habits of contemporary implantable cardioverter defibrillator (ICD) patients. METHODS AND RESULTS: We performed a multicentre prospective observational study of consecutive ICD recipients. Non-commercial drivers with a valid licence were eligible. Patient and ICD data were recorded. All patients completed an anonymous questionnaire regarding their driving habits. Among 275 patients, 25 (9.1%) stopped driving permanently after ICD implantation. During a mean follow-up of 26.5 ± 4.5 months, 25.3% of patients received an ICD shock (52.5% appropriate). The median time to first shock was 7.0 (2.5, 17.5) months and was not significantly different between primary and secondary ICD patients. However, shocks (36.5 vs. 21.3%, P = 0.027) and recurrent shock episodes (17.5 vs. 6.2%, P = 0.011) were more common in secondary ICD patients. Physician-recommended driving restrictions were not recalled by 37.9% and not followed by 23.0% of patients. Overall, the mean duration of driving abstinence was 2.2 ± 2.9 and 3.6 ± 5.3 months for primary and secondary patients, respectively. Notably, 36.5% of secondary patients drove within 1 month. Eight patients (3.3%) received a shock while driving, five of which resulted in road traffic accidents. The annual risk of a shock while driving was 1.5%. CONCLUSIONS: Patient driving behaviour following ICD implantation is variable, with over one-third not remembering and almost one-quarter not adhering to physician-directed driving restrictions. Over one-third of secondary ICD patients drive within 1 month despite physician recommendations. Further studies are required to establish the optimal duration of driving restriction in ICD recipients.

Achieving sufficient safety margins with fixed duration waveforms and the use of multiple time constants.

INTRODUCTION: There are several options to achieve a sufficient safety margin in a patient with a high defibrillation threshold (DFT), with varying and typically modest success. Programming fixed (millisecond) durations of both phases of a biphasic waveform in an implantable cardioverter defibrillator (ICD) has demonstrated utility. METHODS: We established an informal multisite registry of ICD implanting facilities. Each facility agreed to attempt the use of fixed duration waveforms whenever there was an inadequate safety margin with tilt-based waveforms. A 3.5-ms-based fixed duration shock was tried first. If that failed to achieve a 10-J safety margin then a 2-ms-based shock was used. We also tabulated an HEDFT (high estimate DFT) as precise DFTs were not determined. RESULTS: Sixteen patients (15 M, 1 F) were entered into the registry (age 58.2 +/- 17.9 years) with ejection fractions of .30 +/-.11. Superior vena cava coils were used in 7 patients according to physician preference. The tilt-based HEDFTs were 35.4 +/- 3.2 J delivered and 35.8 +/- 3.3 J stored energy. The 3.5-ms based shocks were evaluated on 14 patients and the HEDFT fell to 23.4 +/- 6.3 J delivered (P < 0.0001) and 26.2 +/- 6.9 J stored energy (P < 0.0001). The 2-ms-based fixed duration shocks were then evaluated on 6 patients and the delivered energy HEDFT was 22.2 +/- 5.8 J (P = 0.001 vs. tilt-based shocks) while the stored energy HEDFT was 27.9 +/- 6.4 J (P = 0.01 vs. tilt-based shocks). Using the better of the two fixed duration waveforms, the mean safety margin was improved from -1.2 +/- 1.9 J to 9.5 +/- 5.9 J (P < 0.00001). Multivariate predictors of the safety margin improvement were the absence of the Superior Vena Cava (SVC) coil and absence of Ventricular fibrillation (VF) presentation. Four patients still required lead repositioning after the use of the fixed duration waveforms. No additional leads were implanted. CONCLUSION: The use of a selection of directly programmed fixed duration biphasic shocks had a striking impact on the HEDFT for these difficult patients. Adequate safety margins were obtained for 12 of 16 patients with no lead manipulation or other approaches.

Adjunctive handgrip during dobutamine stress echocardiography: invasive assessment of myocardial oxygen consumption in humans.

BACKGROUND: Adjunctive isometric exercise in the form of sustained submaximal handgrip (HG) is considered to increase the sensitivity of dobutamine stress echo (DSE) for detection of functionally significant coronary artery disease. HYPOTHESIS: The study was undertaken to quantify invasively the impact of HG in humans on hemodynamics and myocardial oxygen consumption (MVO2) during DSE. METHODS: An invasive hemodynamic evaluation was performed during DSE and with addition of adjunctive HG in 11 subjects. Coronary sinus (CS) blood flow, right-sided and systemic pressures, oxygen saturations, and transthoracic two-dimensional echocardiography were obtained at each 3-min stage and after adding HG at peak DSE. Myocardial oxygen consumption was calculated by the Fick method and circumferential end-systolic wall stress (ESWS) by Mirsky's formula. RESULTS: At peak DSE, heart rate, left ventricular ejection fraction, CS flow, and MVO2 increased, whereas pulmonary capillary wedge pressure (PCWP) and circumferential end-systolic wall stress (ESWS) decreased from baseline. Compared with peak DSE, the addition of isometric HG at peak DSE caused an increase in PCWP (7 +/- 3 vs. 8.4 +/- 3 mmHg, p < 0.05), ESWS (112 +/- 25 x 103 vs. 125 +/- 32 x 103 dyne x s x cm2, p = 0.02), and CS flow (260 +/- 92 vs. 301 +/- 105 ml/min, p < 0.05). There was a minimal increase in left ventricular volumes, heart rate, and systolic blood pressure. The MVO2 increased from 29 +/- 8 ml/min at peak DSE to 31 +/- 9 ml/min with adjunctive HG (p = 0.03). CONCLUSION: Handgrip adjunctive to peak DSE results in a modest increase in MVO2, primarily by an increase in end-systolic wall stress.

Tachycardia-induced cardiomyopathy: atrial fibrillation and congestive heart failure.

Tachycardia-induced cardiomyopathy occurs as a result of prolonged, excessive heart rates. Ventricular function may improve significantly upon control of the heart rate. We present a case of a patient with atrial fibrillation with rapid ventricular response who showed a dramatic improvement in left ventricular function following AV nodal ablation and insertion of a pacemaker. We also review the history and pathophysiology of tachycardia-induced cardiomyopathy.

The current status of immune modulating therapy for myocarditis: a case of acute parvovirus myocarditis treated with intravenous immunoglobulin.

We present a case of a patient who presented with a febrile illness without obvious source initially, who developed profound cardiac decompensation and left ventricular dysfunction. Viral titers obtained during the course of illness confirmed parvovirus infection. Intravenous aggressive immunoglobulins and medical therapy for heart failure resulted in stabilization and, ultimately, a complete recovery. Recent data from clinical trials are discussed regarding the utility of immunoglobulins in the treatment of myocarditis and heart failure.

Polymorphic metabolizing genes and susceptibility to atherosclerosis among cigarette smokers.

Atherosclerosis (AR) is the leading cause of morbidity and mortality in the US and cigarette smoking is a major contributing factor to the disease. Like cigarette smoking in lung cancer, genetic susceptibility may be an important factor in determining who is more likely to develop AR. However, the current emphasis has been on susceptibility based on altered cardiovascular homeostasis. In this investigation, we studied 120 AR patients and 90 matched controls to elucidate the association between polymorphisms in some metabolizing genes (GSTM1, GSTT1, CYP2E1, mEH, PON1, and MPO) and susceptibility to AR. We found that the GSTT1 null allele and the fast allele of mEH(*) (exon 4) are associated with risk for AR. Furthermore, the combined genotypes GSTM1 null/ CYP2E1(*)5B, GSTM1 null/mEH YY, and GSTT1 null/mEH YY are significantly associated with susceptibility to AR (OR = 15.42, 95% CI = 1.33-77.93, P = 0.021; OR = 3.48, 95% CI = 1.63-8.04, P = 0.0008; OR = 3.4; 95% CI = 0.99-17.38, P = 0.05; respectively). We have also conducted cytogenetic analysis to elucidate if induction of chromosome aberrations (CAs) is a biomarker of AR susceptibility. We found that among cigarette smokers (AR patients and smoker controls), individuals having the GSTM1 null allele had a significantly higher frequency of CAs compared to those with the normal allele (P < 0.05). This association was not found among nonsmokers. In addition, individuals who had inherited the CYP2E1(*)5B allele exhibited a significantly higher CA frequency (8.0 +/- 0.82) compared to those with the CYP2E1 wild-type genotype (4.31 +/- 0.35). Since the analysis of genetic susceptibility factors is still in its infancy, our study may stimulate additional investigations to understand the roles of genetic susceptibility and cigarette smoking in AR.