Paroxysmal Heart Block and Ventricular Standstill.

In auriculo-ventricular block the degree of impairment of conductivity is often found to be inconstant. Even at a time when the rhythm appears clinically to be normal, however, a cardiogram will usually show prolongation of the P-R interval. Only rarely is the conduction normal between the attacks, and the term " paroxysmal heart block " may then appropriately be applied. Reports of 18 such cases have been found, 7 of which had periods of ventricular standstill also; in addition, we found 3 cases of paroxysmal ventricular standstill without heart block (see Starling and Lewis, infra). Hay (1906) described a case in which occasional ventricular beats were dropped, despite regular auricular contractions as shown by the polygraph and unimpaired conduction in the remaining beats; he suggested a depression of ventricular excitability as the cause. His patient was a man of 65 with hypertensive heart disease, and partial heart block had been present in a previous tracing. Gossage (1909) described a similar condition in a woman of 71with hypertension, and considered it an intermittent form of heart block. In a case recorded by Macintosh and Falconer (1910), a man of 74 had periods of ventricular standstill with Stokes-Adams seizures, during which the auricular rate gradually accelerated, slowing again when the ventricular contractions returned; they were abolished by atropine. Periods of complete A-V block and also of high-grade partial block with a slow irregular ventricular beat were encountered at times. Between attacks, the a-c interval was normal. Starling (1921) reported the occurrence of periodic ventricular standstill with Stokes-Adams attacks in a man of 51 with a normal-sized heart and a blood pressure of 160/110. Conduction was unimpaired in the intervals. Swallowing used to bring on an attack, but not if atropine had been given during the previous hour. Complete heart block finally supervened. RussellWells and Wiltshire (1922) described a male, aged 58, with intermittent complete heart block. The conduction was normal in the intervals. Infective endocarditis was found post-mortem and calcification in the region of the A-V bundle. In the case of Gage and Pardee (1925), a man of 59 with arteriosclerosis, there was intermittent complete block and at other times intermittent ventricular standstill. Conduction was normal in the intervals. Atropine was without effect but adrenaline was followed by ventricular tachycardia, ventricular standstill, and death. Post-mortem, the mitral valve was found to be calcified. Lewis (1925) mentions two cases of intermittent ventricular standstill in patients with normal A-V conduction, in one of which the fibres of the bundle were found to be separated by large venous sinuses. Yater and Williams (1928) described a man of 74 with arteriosclerosis who had periods of normal rhythm alternating with 2: 1 heart block, complete heart block, and ventricular standstill; post-mortem, there was calcification in the interventricular septum at the junction of its membranous and muscular parts, and invasion of the bundle of His by fibrous tissue. In the case recorded by Wolferth and McMillan (1928), a woman aged 48, periods of partial and complete block were interspersed with normal rhythm during which conduction was unimpaired. Even during phases of partial block, the P-R interval was normal. Atropine