There are dozens of Long QT types but over the last few years some have been found to simply be natural heart responses to extreme circumstances. The genotypes (different gene mutations) can have thousands of phenotypes (presentations). This can be because the human genome is massive so even within the same gene (let’s say SCN5A) the mutation can occur anywhere along this sequence and that affects how severely the condition presents itself. So Isla’s SCN5A mutation caused a very dangerous form of Long QT 3, whereas someone with a maybe smaller or mutation somewhere else in the SCN5A gene, may have a less severe phenotype of Long QT 3.
The Long Cutie 